If you think its dirty, you can always suggest taking a shower together. Get him all nice and lathered up. I'm sure he'll appreciate anything at that point. The issue of semen is a bit different. I'll admit semen does seem a bit gross, but really it's not that bad.
Many women feel that it is disgusting.
One solution is to try to prevent as little as possible from getting to your mouth in the first place. I think that Nubile Ho has some good advice for you on the other side of things. Nubile Ho Dude, most people don't like eating fruits and vegetables either, but we do it for the sake of our health. Pretend that you are on a diet, and your man is a protein shake. For example, strawberries, wine and champagne can give it a sweeter taste.