I don't think anybody thinks they should be obliged - I certainly don't. What I DO think is that, given how long they had known her, and what they knew of her character, should have made them at least wonder - 'why does she think that?'. Maybe even have a conversation. Instead, they jumped straight to public condemnation and attack.
Particularly with Watson, there was a whiff of bandwagon-jumping - I never felt there was any sincerity in her TWAW pronouncements, it was all a bit performative in my opinion - the fawning over Paris Lees being a good example. Radcliffe was coming from the position of being entwined with, and schooled by, a trans-cheerleading charity. I felt he was more sincere in his belief, but still find the lack of any sanity-check in his thinking (is this really a good idea?) contemptible. In our society, celebs have too much influence. Children in particular are swayed by what they do/say/wear. That alone, plus the extra influence they had as 'Harry' and 'Hermione' should have nudged them into exercising their influence more cautiously. Instead they went for broke.