Sorry, I'm not seeing the sexism, it could just have easily been a 'we've seen your penis' song, which would also have been funny but due to lack of penises onscreen, it makes more sense to go with the much more commonly flashed boobs. I can't think of a greater complement for an actor than to be in an Oscar song, it shows they've made it.
It's juvenile humour (hilarious to those of us who like that sort of thing) which is what you expect from the creator of family guy and ted!!! Not everybody's cup of tea, fair enough but complaints of racism, sexism, homophobia and god knows what else are ridiculous and false.