I don’t think I have to expand on that.
Same goes for sexism, ageism, etc etc.
I used to crack jokes about black people back in college (of the same character that ugh linked to) - I didn't think it was racism, after all I didn't actually have anything against black people, right? Then I graduated, moved to another city, and made a lot of black friends that bucked the stereotypes so dramatically that now I find the same jokes at least mildly offensive.
Racism is a spectrum, it isn't as binary as "lynch 'em" vs. "I love them", there are many shades of gray, and many places where you're subtly contributing to it by believing in, and spreading extremely damaging stereotypes.
Second, it’s indistinguishable from what a racist would say. There is no subversion.