Well, that's fine. No one is calling for him to be jailed. He's just being stripped of a humanitarian award, which, if he opposes social justice activism as you say, makes perfect sense.
But Dawkins just asked a question. Why is asking a question equivalent to "opposing social justice activism"?
Perhaps more importantly, people disagree about the nature of real "social justice".
Let me give an example. Some people think trans-women should be allowed into female sports as this is the inclusive, fair, non-discriminatory thing to do.
Other people, however, are going to think that's not a real "social justice" cause at all. Quite the opposite. That's a violation of women's traditional sex based rights, and takes opportunities away from biological females. One of the major reasons we separated sports by sex in the first place is it's simply not a fair competition.
So if you say to person X, that we are kicking you out of a humanist organisation because "you don't support social justice activism", you may just be begging the question over what real "social justice activism" happens to be in this case.
If you start insisting that you have to have all the right ethical opinions to qualify as a "humanist", then it actually looks like that undermines/contradicts humanism. It's rather turning itself into a sect of supposed "humanism" where you aren't allowed to ask questions which may upset the orthodoxy.