Honestly I think Chris meant that he had literal dreams about having sex with his mum, not that it was an actual ambition of his. It's still wrong and extremely strange to dream it to begin with, but he never actually acted on them which at least is saying something. I know what he's saying is still gross but it's easy to get caught up on what he's saying and believing it to be worse than it actually is.
God, I can't believe I'm having to rationalise Chris saying he dreamed of having sex with his mother. I know he thinks he's a great mind who has tonnes of readers hanging on and agreeing with his every word but this is one time I wish he'd known when to just shut up.