interracial porn is frequently used by the alt-right racists to point out the evils of "race mixing" and to blame jews for being the producers of it. It is not an anti alt-right point at all.
Even if its posted by someone that is against the alt-right, it becomes a post to unify alt-right users.
It’s because they sexualize their fears. A lot of real fear of the BBC from scrawny white kids there.
Also why cuckolding, and other very embarrassing (for men) fetishes are popular there.
I unironically worry more about the degenerate fetishes that 4chan spreads more than the dumbass political ideologies they purport to have. Americans views of sexuality is so warped and sad because of mind viruses like this.