I have a confession. I used to find Jacob Rees-Mogg amusing. Who wouldn't? He campaigned with his nanny. He has an improbable number of children, many with improbable names. His wife is called Helena de Chair. He once filibustered a bill on sustainable agriculture by talking about a fictional pig from the novels of PG Wodehouse. ("I had hoped that someone might mention the Empress of Blandings, the only pig in history to win the silver medal at the Shropshire show for three successive years. It ate a vast quantity of potatoes every day and was more than happy to eat waste food. If we are not careful, however, we will risk reintroducing problems such as foot and mouth disease, which cost the country, the taxpayer and Her Majesty's Government billions of pounds to put right.") In the tragicomic world of the House of Commons, this counts as Top Banter.

The problem is that modern politics is a series of jokes getting out of hand. We have a foreign secretary who every other country finds ludicrous, put there because he can quote Jeeves and Wooster and was quite good on Have I Got News For You a decade ago. (Thinking about it, the collected works of PG Wodehouse have a lot to answer for in the creation of the current Tory party.) Simply by holding a pint and laughing like Sid James, Nigel Farage neutralised the menace of posters warning of "Breaking Point" and soundbites about how migrants spread HIV. A whole swathe of politicians are painfully, icily courteous, as if that means that they can't possibly support terrible policies and anyone who disagrees is incredibly beastly and rude.

Last year I wrote a long piece for an American magazine about how the US and UK media had failed to give readers and viewers good information about the EU referendum and the US election. One of the most striking quotations came from the New Yorker writer Evan Osnos, who followed the Trump campaign and interviewed his supporters extensively. "For many months there were reporters who were still too light-hearted about the Trump phenomenon, long after it should have been plain to them that it was not remotely funny," he told me. "It was a mistake to allow him to go on television, month after month, phoning into interviews that would ordinarily require the person to be in the studio and subject to the kind of scrutiny that an in-person interview produces. But instead, because he was treated as something between a joke and a boon for ratings, he was allowed to call in. That was an abdication of responsibility."

Exactly the same pattern has been repeated with Rees-Mogg. He is the butt of panel show jokes; the "colour" booking on political discussion shows; the subject of ironic memes. Wouldn't it be funny if this old-fashioned dude was a viral internet phenomenon? Well, no.

As a result of his raised profile, on 12 July Rees-Mogg got 226 votes in the race to chair a select committee. (He was beaten by Remainer Nicky Morgan with 290.) He was mentioned in stories about an upcoming Tory reshuffle on Monday, then went on the Daily Politics to steer a careful line between suggesting he might accept, but also stressing his deep Leave credentials and his innate rebelliousness. The Conservatives aren't exactly drowning in oven-ready leadership candidates, so it's not surprising he topped a poll by Conservative Home over a successor to Theresa May.

A candidate from outside the party's mainstream, who has long made a virtue of rebelling against the whip, who is chosen by pissed-off activists to give the rest of the candidates and the establishment a good kicking? Well, that could never happen.

On ITV this morning, Rees-Mogg told Susanna Reid and Piers Morgan that he was "completely opposed" to abortion, because "life begins at conception". He is also against gay marriage. These are not just personal views (as you might have argued in the case of Tim Farron). He has consistently voted in line with his conscience. He has also consistently voted in favour of welfare cuts, against higher taxes on bankers, against smoking bans, for more private involvement in the NHS, and against a wholly elected House of Lords. This is not banter. This is everything progressives have fought against for 50 years.

How droll, some might still think. Wouldn't it be funny to watch Labour smash this guy at a general election! I hear that view, and I think of poor old John Oliver urging Donald Trump to run for president because it would be funny to see him get creamed. British politics is wildly unpredictable. If Rees-Mogg made it to the final two in a Tory leadership race, against a Remainer, would the party's right really hold their noses and vote against him? And even as a cabinet member or leading backbencher his views gain a huge aura of legitimacy. He's perfectly entitled to them, of course, but is that really the message the Conservative wants to send in 2017?

Don't fall for He's-Just-One-Guy-ism, either. Any restrictions on abortion, for example, are unlikely to come in the form of a bill calling for it to be banned; there would instead be a US-style push to chip away at access. Or an announcement that "new science" means that the limit needs to be reduced. As Fiona Bruce's attempt to use sex-selective abortions as a wedge issue in the last parliament shows, a single parliamentarian with a good grasp of procedure can be very effective.

Ultimately, Tories will do what they want to do without paying any attention to the likes of me. The left needs to be clear on its response, though. It feels as though we have learned absolutely bugger all from the lessons of the last few years. Don't patronise people you disagree with; argue with their ideas, don't mock their affectations or accent. Don't treat someone as a joke right up until the moment you try to warn people their views are dangerous: the Conservatives tried it at the last election with Jeremy Corbyn, and it patently didn't work. There's no reason it should be effective against a right-wing politician, either.

Liberal, progressive politics have not secured such a perpetual triumph that the luxury of lazy condescension can be indulged. Jacob Rees-Mogg is not Boaty McBoatface. If his views gain legitimacy, real lives will be affected. I don't care if he rides a god-damn unicycle down the Mall while wearing a Victorian bathing suit and a monocle, and quoting bits of Toad of Toad Hall. Treat him with the seriousness his views deserve.

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Now listen to Helen discussing Jacob Rees-Mogg on the NS podcast: