"Thou shalt not strike terms from others' expressive vocabulary without suitable replacement." - me

Suppose your friend says: "I don't buy that brand of dip. It's full of chemicals."

Reasonable answer: "I'm skeptical that any of them are harmful in these quantities; we don't have much reason to believe that."

Reasonable answer: "Yellow 5? Are you allergic?"

Reasonable answer: "Okay, let's get the kind with four easily recognizable ingredients."

No: "Technically, everything is chemicals. Dihydrogen monoxide!"

Pedantry is seldom a way to make friends and influence people, but this example particularly gets my goat because there doesn't seem to actually exist a word in English for the thing you know perfectly well people mean when they say "chemicals". When I tried to find one on Twitter, the closest options were "toxins" and "additives". But neither is right. "Toxins" excludes yellow 5 - or, whether it does or not might be a point of contention; but it isn't the thing originally expressed with the word "chemicals". People may want to avoid - or otherwise discuss - "chemicals" for reasons other than thinking they're literally toxic; if I tell a maid I'm sensitive to chemical smells but vinegar is okay this is useful information. "Additives" includes, say, added sugar, which, while a plausible complaint, is a separate complaint.

Suppose your grandma says, "Okay, no technology at the dinner table."

Reasonable answer: "I'll put the laptop away to make room for the potatoes, but I need the phone because I get anxious without it."

Reasonable answer: "Sure, Grandma."

Reasonable answer: "We can try that until Uncle Bill starts making easily falsified claims about Flat Earth."

No: "Technically, the dinner table is a technology. And so are your glasses, Grandma."

In this case a more precise word exists - "electronics" ambiguously includes the chandelier but at least firmly sets aside the question of whether your grandma wants you to eat naked and with your bare hands. But refusing to know what she meant because she could have gotten closer to saying it, not even literally (she isn't being metaphorical), but technically, pedantically, definitionally? This is both a bad social move and a bad epistemic one; you're having the conversation on a level that is wholly about verbal wallpaper. Do you prefer to say "electronics" or dip into synechdoche with "screens" or spend nine syllables on "internet enabled devices"? Are you actually unsure if your grandmother wants you to set aside your smart watch, dumb phone, or electric blanket of intermediate intellect? Use your own words, ask your own questions, but don't enforce an inadequate prescriptivism with feigned incomprehension while your interlocutor only wants you to pass the peas.

Thou shalt not strike terms from others' expressive vocabulary without suitable replacement. It's a pet issue of mine; it's my pinned tweet. "Suitable replacement" means suitable across the board, Pareto improvement as seen by the user along every axis a word can have. I think people are within their rights to reject a proposed replacement for not meaning the right thing, sounding ugly, being one syllable longer, being hard to spell, not rhyming in a poem they're trying to write, and vague gut feeling that you're just trying to control them. I extend this as far as "gypsy" and "Eskimo", at least (and with slightly less fervor to a slur beyond that if you really don't have another term for Brazil nuts).

Suitable replacement is a very high standard. It has to be. If you take someone's words away - and refusing to understand them when the problem is not in fact in your understanding does that, since words are tools to communicate - they are very direly crippled. Many people think communicatively; while you might not be their only outlet for working through their ideas, social shame for imprecise language can do your work for you across the board if you hit someone vulnerable hard enough. If you offer them worse words instead of expecting them to guess, they might only be crippled to the degree of wearing uncomfortable shoes, but that's still too much. Don't set up shop a block farther away than you had to and dress code folks for wearing Crocs. Communication is already difficult.

Some things I am not saying:

you, yes you, have to talk to people who use words you can't stand or in ways you can't stand

Nah. Block people on every website you use over ship names and disown your sister for saying "moist" for all I care. You also have my blanket permission to use any sarcastic defense mechanism that works for you against your abusive parents if you have those, or whatever.

you should not offer people better words for whatever value of "better"

By all means offer. "I think the preferred term is 'transgender' this week." But if they can't abide the difference in shade of meaning or mouthfeel, maybe even if they overtly announce it's just because they want to call it like they see it and they see it in some horrid way, don't try to correct them by pretending to be missing that section of your dictionary when you really aren't.

Humpty Dumpty was right, words mean whatever the speaker wants them to mean, all is descriptivist chaos, "literally irregardless"

No. My examples have in common that they point at things and you can tell what things they are by being a speaker of the language in the conversational context. If someone starts calling cardboard boxes "pants" for no reason they're just wrong and you don't have to learn their stupid code.

Edit 12/2019:

sirjackholland wrote a comment, now slightly buried, including this paragraph:

But I genuinely don't know what "natural" is supposed to (approximately) carve up, especially in the realm of foods. If you boil tea leaves, are the resulting compounds natural? If yes, then at what point do things become unnatural? If no, then is anything that's not raw and unprocessed unnatural, including e.g. cooked meat or boiled potatoes? There is clearly a spectrum between "raw and unprocessed" and "industrially engineered" but I don't see any reasonable place to draw the line. And this makes the word "natural" in the context of foods too vague to be useful - every time someone uses it, you have to ask a series of followup questions to figure out where they (arbitrarily) draw the line.

To which I replied:

I want to point out that there are lots of situations where English speakers fluently use words that don't have clear dividing lines between their applicability and their inapplicability - it depends on context and details. "The music is loud." What if I'm deaf or far away or like to be able to feel the bass line in my bones? That doesn't make the sentence impermissible or even hard to understand and I don't need the speaker to produce a decibel value. "If you go to high altitudes, the air is thinner and you might get dizzy." How high? If I'm dizzy in Denver and the speaker thinks you shouldn't need to adjust your behavior until there are Sherpas about and meanwhile Batman can breathe in space, that doesn't make the sentence false, let alone useless. "It's cold, bring a jacket." Oh you sweet summer child, I'm good in short sleeves, thanks, I just don't know what you meant by "cold" -

There are lots of conversational purposes for which you don't in fact have to know where someone draws the line. You don't even need to be able to agree on every point's ordering in the spectrum ("it's colder today" "that's just windchill"). The words gesture in a direction. I think "chemicals" does too, and you know what direction because you came up with "unprocessed" as a gloss on "low in chemicals". If someone doesn't buy that brand of dip because it's full of chemicals, in your innocent confusion I suggest you glance at the ingredients list for a guess at the threshold in question.

In the linguistic sense, a term's use can be "felicitous", without it having to be precise, literally accurate, etc. If you don't know what a word means but you know what spectrum it's on... that suggests that actually you know what the word means.