It’s that other people can see it.

Filter lists for one’s own experience are not the goal of that outrage. Keeping certain information from spreading to others (controlling what third parties can see) is the desire.

The censorship urge is not “I am offended by this”, but more “if my neighbors read things like this, I am afraid”.

I think it stems from a low-trust society and the assumption that the median members of society lack critical thinking skills.