Watching the new season of the TV sitcom Roseanne, which rebooted in the US last month after a 20-year hiatus, has been like finding an old school friend on Facebook: full of affection and nostalgia and thrilling suspense as one waits to discover if she turned out to be awful. In the case of Roseanne Barr, that question had already been answered in pre-publicity for the show in a way that, for many people, left no room for doubt or discussion: Trump supporter, case closed.

Many of Barr’s old tweets have been deleted, but for a while she was a reliable disseminator of nutty pro-Trump conspiracy theories

There is something inherently amusing about raising the Wagner/TS Eliot question – can one admire a piece of art while despising the artist? – about a sitcom. Not to denigrate the form, exactly, but the Conners’ iconic crochet-covered couch has never seemed so bathetic. The first two episodes were funny, charming and clever. Roseanne was sly and arch, as one remembered her to be, showing us that with a better haircut, a 65-year-old can look younger than she did at 40. Sara Gilbert’s Darlene was adorably sour; Jackie was, as ever, sublimely played by Laurie Metcalf; and Dan was Dan. And then there was Trump.

“What’s up, deplorable?” says Jackie, dressed in a pink pussy hat, the words “Nasty Woman” emblazoned across her T-shirt as she greets her sister for the first time since the election. Barr herself has presented the show’s political positioning as a potential act of reconciliation along the lines of, why can’t we get together and laugh at our differences?

And the political jokes, although the most strained of the script, did feel somewhat cathartic. Roseanne gets in inevitable references to snowflakes; Jackie brings Russian salad dressing for dinner. Watching the show felt like that rare thing, a place where both sides could hang out.

The problem, obviously, is Roseanne herself. Choosing to make Roseanne Conner a Trump supporter was a smart dramatic choice, and a plausible one too, but it does leave one wondering about the politics. Onscreen, she is charming and reasonable (“He talked about jobs, Jackie,” Roseanne Conner says desperately to her sister of why she voted for Trump); the palatable face of an ugly political movement. In real life, or at least on social media, Roseanne Barr has a significantly less amenable presence.

Many of Barr’s old tweets have been deleted, but for a while now she has been a reliable disseminator of nutty pro-Trump conspiracy theories and a general amplifier of the lunatic fringe. In a bad-tempered interview with the New York Times last month, Barr said it was her idea for Roseanne to back Trump, “because it’s an accurate portrayal of these people and people like them”. But by the standards of her own Twitter output, this isn’t quite true.

Trump rang to congratulate Barr on the ratings – 18.2 million for the debut episode, so the series has already been renewed for a second season. She was purported to be thrilled by the call, and that soured the good feelings many had for her coming out of the show.

And yet the show is still good. Writing a hit clearly matters more to Barr than politics and, to that end, Roseanne is not a propaganda piece. It works artistically because it is rooted in something Twitter personas can’t get at: the humanity of the other side.

• Emma Brockes is a Guardian columnist