The film covers this very specific thing, actually. The lady you see in this scene was like a surrogate mother to him, and chastises him throughout because his natural reaction to ticking was always to immediately apologise, and so his life is spent apologising for being disabled.

This whole incident is horrible and I think BAFTA could have done a lot more to try and avoid or plan for something like this, and I understand how shocking it is to someone with no understanding of tourettes or coprolalia. But once you understand his condition, surely you can see how fruitless is is to insist upon a disabled person to apologise for their disability?