If a liberal tells a "racist joke" its considered post ironic?

But if some bloke scratching his on a building site tells the same joke its considered racist, where when and how did this happen? Jerry Sadowitch a comedy genuis would invite people to berate him about being jewish " he says aye don't forget i have a big nose and curly hair as well" in his Glaswegian brogue. Liberal he aint, he's a comedian thats his job to make people laugh. But i don't understand how "comedians" can say one thing and be allowed off with it. If Jo Brand was skinny and worked working mens clubs and said half the stuff she gets away with now she'd be called a racist or worse.