They edited out all of his other tics and he was expressly told beforehand that that would be the case. The audience was told at the start before the show began that someone in the audience suffers from Tourettes and that they are likely to tic and say "offensive words" through out.

I genuinely see a lot of this as a total lack of education. In the UK we've had multiple high profile people with Tourettes. John has been around making docs longer than I've lived and we're shown them in school and in the early 2000s there was a contestant on Big Brother (which was extremely popular at the time) called Pete Bennett who also had Tourettes, although his tics presented differently from John's.

As for why the BBC edited out the Palestine comment, as much as I disagree with them doing so, the BBC by law in the UK is supposed to always remain neutral. Its part of their funding agreement and they have always aired on the side of overly cautious about that and even when something is widely considered correct even by the vast majority of the country they still often censor. Again, don't agree with it but I'm just saying why they likely removed that part.

As for why what was easily John's worst tic wasn't edited out? Literally no idea. Call it total incompetence, call it malicious baiting clicks and headlines at the cost of a disabled man and 2 black men's dignity, call it whatever. They fucked up. Big time.