Google/Twitter/Facebook/Reddit are private entities that own their platforms and can enforce rules there.
There are private entities, public corporations and government.
We hold government to highest standard of equality, we give private entities most freedom to discriminate. Public corporation with share holders are held somewhere in between.
Your friend can kick a person spouting white separatist views out of his room. Good call, in my opinion, by your friend.
Should Mead, makers of paper notebooks, have a right to see what someone has writing in a notebook and take away the notebook if they don't like what's being written?