In their minds certain groups (fill in the blank with the usual suspects) are oppressed by whites/society. Therefore speech that is in any way supportive of oppressors doesn't need to be on the wall because oppressor speech is already pervasive in society, and the oppressed groups are lynched for speaking out.

There was an article about an anti free speech professor on reddit KIA some years ago. The professor couldn't fathom that there wasn't free speech because they had pro LBGT slogans on their door. It took me some time to realize what their thought process was.

But you are right, their worldview is so warped that they no longer understand what free speech is, and they now believe the RVO part of DARVO that they can't see it anymore.