So why is there so much racism, doxing, and other horrible behavior? Or are only some of the boards moderated?

All boards are moderated in a completely different way. Most of the boards have a pinned post with the rules. Most moderation occurs stealthily.

Also, racism and doxxing are not comparable at all.

The double-edged sword of not moderating based on racism and other undesirable behavior is that your job as a moderator is much easier, but you have the terrible reputation that 4chan has. I am personally fine with boards that allow pretty much everything other than CP and other illegal content. I think this is how a number of chan boards operate.

Do they both not belong to "horrible behavior?"