And should you insist on this to the point of getting thrown out of a cafe?

IMAGINE you're ordering a bagel. You say to the counter person "I'd like a bagel." The helpful young wage-earner asks, as required by the bosses, "would you like butter or cream cheese?" Do you

a) say "no, thanks. Plain."

b) Throw a fit, saying that if you had wanted butter or cream cheese you would have asked for it, and that the fact that this obvious logic was not understood illustrates the bad grammar of the staff, tout the importance of correct language and, sticking relentlessly by your position, eventually call the staff person an "asshole" until you are thrown out?

If you're a competent English speaker, you chose "a". That is because use of language entails understanding not only how sounds, words and grammar work, but also social convention, appropriateness, shared background knowledge and culture all contribute to the use of language. If you're Lynne Rosenthal of New York, you chose B.

Ms Rosenthal, who has a PhD in English, explained herself by saying "Linguistically, it's stupid, and I'm a stickler for correct English...They don't understand what a plain multigrain bagel is." I'm sorry, Ms Rosenthal, but linguistically, your position is stupid hovering just above insanity. Most 21st century Americans understand that when ordering take-away food at a counter, you will often be asked if you want various options. This is not limited to Starbucks. The competent thing to do, bringing all your meta-linguistic skills (the study of which is called "pragmatics") to bear, is say "no, thanks". Only someone whose pragmatic skills are severely impaired—some people with autism-spectrum disorders like Asperger's have trouble with this, for example—lose the plot and insist on a pseudo-logical argument that "a bagel" logically excludes "a bagel with butter", making the question "would you like anything else?" an affront.

The story reminds me of a bartender in my university days who would reply to "I'd like a beer please" with "I'm sure you would". He would sit there smugly until you said "Give me a beer, please, and I will give you some money" or some such. It was asinine; he was showing how little, not how well, he understood how language works. Such inanities violate the co-operative principle (illustrated in comic form here) that underlies successful speaking. People don't talk like computers ("give me the set of objects that includes a bagel and only a bagel", "if you meet the condition x where x='giving me a beer' then I will undertake action y where y='giving you two pounds ten'.") because they don't have to. And it's unpleasant to do so.

For what it's worth, I'm with Ms Rosenthal on the Starbucks coffee sizes. It's silly to call a small coffee "tall". Doing my little part for plain English, I always just ask for a small. But I don't huff and puff, and the staff understands me with no trouble. I get what I want, avoiding confrontation. Acting like Ms Rosenthal violates not just the co-operative principle but the Walter Sobchak principle. Life is too short for that.