The Battle for Barking, More4, Tuesday</br> Frankie Boyle's Tramadol Nights, Channel 4, Tuesday

Anyone of a sensitive disposition would have had a rough time in front of the telly last week – between getting up close and personal with the British National Party and jokes equating religious faith with mental illness, there was considerable potential for offence.

More4 documentary The Battle for Barking, which followed the run-up to this year's election contest between BNP leader Nick Griffin and Labour's Margaret Hodge in the east London borough, contained more expletives than an episode of Shameless. Most came from local residents (black, white and Asian alike) outraged to see the BNP campaigning on their streets, but Hodge was responsible for at least a couple in her unscripted reaction to the news that Griffin would be contesting her seat.

Studiously even-handed, the film silently added weight to the argument that depriving the BNP of a public platform only serves to further their cause – given 90 minutes of televisual rope, Griffin and co did a brilliant job of hanging themselves as credible political contenders. It didn't help that Griffin, who has a face for radio and oratory skills for silent film, seemed to have a cake welded to his hand in all situations – evidently multiculturalism is OK by him if it takes the form of a Danish pastry.

Embarrassingly amateurish, the BNP couldn't even nail the empty rhetoric. Rallying a party meeting, one councillor bombastically declaimed: "You must give your hearts, you must give your souls to this – five days a week!" Well, no one wants to go out stirring up racial tension when X-Factor's on.

But for all their inadequacies, they had Hodge worried. Her canvassing slogan quickly went from "Vote Labour!" to "Anybody but the BNP!" and it was on the doorsteps of Barking that the programme's most pressing question was answered – why do seemingly normal people vote BNP?

Everybody was at pains to stress that they weren't racist and, on a fundamental level, I believed them. Immigration had simply become the prism through which local and national ills – namely unemployment and a chronic shortage of social housing – were being refracted. Add to that a pervasive sense that those at the top simply didn't care and the crude appeal of the BNP as a party "of the people" became clearer.

Given that we knew only too well that the programme would conclude in the satisfying trouncing of the BNP, I wondered why I felt a growing knot of anxiety in my stomach as I watched. Perhaps it was the realisation that, even if the BNP has been temporarily cauterised, we still have a long way to go before we're safely beyond the situation of which they took advantage.

It's a shame Hodge couldn't have enlisted the services of Frankie Boyle as part of her campaign; in his new series Tramadol Nights, the notoriously abrasive comedian, who rose to fame on BBC2's Mock the Week, demonstrated that he can make mincemeat of anyone, with a mere one-liner.

"You look like a child's drawing of a dead baby," he told one member of the (presumably masochistic) front row, but that's practically a compliment from Boyle, who has found himself in hot water before for making fun of people with Down's syndrome, and comparing Olympic swimmer Rebecca Adlington to "somebody looking at themselves in the back of a spoon".

Boyle's modus operandi – a mixture of stand-up and pre-recorded sketches – is to say the unsayable. It works best when he is having a pop at something monolithic enough to take, or indeed deserve it, so the best of the sketches were those that satirised the bland inanity of TV culture. In a dark send-up of the hidden-camera reality show format, a man has to convince his friend that he has accidentally killed someone.

I'm less comfortable with the jokes about mental illness – in this episode more or less restricted to crude impressions conflating religion and autism. Here it's not at all clear who or what Boyle is targeting – is it political correctness, or our own prejudices? Whatever his intention, the net result feels too much like an unenlightening mocking of difference.

Boyle's one-liners are, in fact, his strong suit, the vitriol often counterbalanced by sheer verbal flair. But on the whole there's something very brittle about the laughter. The world seems a meaner place after listening to Boyle.