Racism is bad, though. It's unfair to judge something for something they were just born with, that isn't their choice. Please share why you think judging someone for their race (which they did not control) is ok. Unless you meant by your post that 'leftists' (I honestly don't know who you're referring to) think that racism is bad, and you do too.
The problem is that right wing jokes aren't funny. The right is delicate and gets butt hurt by left wing humour. Lacking critical thinking skills they assume that humour just involves hurting the other side, since they are hurt, and therefor just try to hurt the left and end up coming off as humorless dolts.