Well some of those ads break the law where I live. I'd rather not go to jail. The one I got an apology for was go-to-jail material: an actively prosecuted topic.
Moreover most of those ads are not good for the long term relationship I want with my visitors. So while in the short run it might mean a very small decrease in revenue, in the long run I'm the clear winner by blocking all the crap (and I'd love to be able to block even more e.g. anything mentioning "free", or anything leading to sites with downloads on them).