Real racist jokes or sexist jokes aren't funny - not because they're offensive, but because they're not true. As soon as a joke is based on an untruth, it's not funny.
To me, racist jokes are not funny. I am politically correct, in a weird way. I like to push the boundaries that are politically correct.
I learned all those jokes in second grade. Second grade is really where they tell you those horrific jokes, racist jokes and misogynistic jokes that you have no idea what they mean, and you just memorize them because they have a very strong effect, they make people laugh in this kind of nervous, horrible way, and it's only later that you realize that you've got a head full of crap.