Almost everyone was vicious about the sitcom Vicious (STV, Monday, 9pm) when it was first shown in 2013, so vicious in fact that I felt a little protective towards it.

Some said a seemingly liberated sitcom about two older gay men, played by Ian McKellen and Derek Jacobi, was a little bit homophobic and a little bit 1970s; others said it was unfunny, nasty and cruel.

However, as far as I could see after watching a few episodes, the critics were missing the point. It may be called Vicious but the show could just as easily have been called Fragile, or even Vulnerable, because under all the viciousness, that's what every character was. Once you see that, you can't help feeling a little warmer towards the show.

To really enjoy Vicious, you also have to make a political adjustment or two in your head because this is a gay show being made in a post-gay-revolution, post-equality society. There was a time, 20-30 years ago, when gay people on television were, without exception, ridiculed, parodied, mocked or attacked. Then there was a time when equality was advancing quickly and no one would say anything critical about gay people or gay culture.

But now we are in a third, much healthier, post-equality phase in which gay people can be mocked just as much as straight people, which is how it should be, and Vicious really goes for it. Sadly, some of the critics were a little behind the curve on this and saw the jokes as a throwback to the gay cliché of the 70s when what they were really seeing was a bit of gay fact. Like it or not, there is a certain type of gay man who can be bitchy, confrontational, and conservative (and Conservative). Ivan Massow, one of the candidates for London mayor, was definitely on to something recently when he said that, of all the political parties, the Tories are the gayest.

Both McKellen and Jacobi's characters fit this mould and are deeply conventional, as are some of the jokes. "I will segue into a whole new range of roles," says McKellen's character Freddie, who's an actor. "Yes," says Jacobi's character Stuart. "Corpses." The set-up of the first episode of the new series, in which Stuart had to pretend to be married and Freddie had to pretend to be his butler, was also pretty conventional stuff, and will be a familiar structure to anyone who has watched even a few sitcoms.

However, the performances always outshine the sometimes conventional plots and set-ups. Both McKellen and Jacobi have the volume and brightness turned up to max and seem to be delighting in ditching all the subtlety for which they're famous. Frances De La Tour, as their friend Violet, is also wonderful in her old familiar role of the lascivious singleton. Velvety and cushioned, she is like an elegant chaise longue reclining on an elegant chaise longue.

Some of the jokes may take a bit of getting used to but that's because they are delivered with such unforgiving sarcasm and a wit that's been sharpened by all the years of being used as a weapon of self-defence. But there's progress in this show. There was a time when gay men were the jokes; now gay men are cracking them, publicly, unapologetically, honestly and a little bit viciously.