The word is "tired", I think. A lot of people just don't have the energy to answer the whys and are used to bad actors using why to exhaust them. So when it comes to things like racism, sexism, homophobia, transphobia...etc.. it's a) an exhausting subject to begin with when its aimed at you, and b) a magnet for disingenuous bigots and trolls, so people will just shut down the conversation rather than try and explain their whole existence.
Honestly, I think isms are the only times when sealioning is sealioning, because that's the only time you get people arguing in such bad faith.