Other than the gay guys that don't like girl-girl action, there are a few guys that don't enjoy it for other reasons.
I knew a guy that was all into it with his wife. The couple had a kid and were very happy together, and decided to get with another girl. Well.... to make a long story short, she left him for the other girl and took the kid. Now, he's paying child support and doesn't get to see his kid very often. ..... He hates lesbians now (duh)
Another friend of my dad's had 6 kids with his wife, and one day she decided that she was bi-curious and he thougt it was wrong to sleep with someone while they were married so nothing happend. Later, one of her friends (who was lesbian) got evicted from her house and stayed with them for a few weeks. One night my dad's friend woke up and his wife was not in bed.... he went to the other woman's room and found his wife there getting it on with her. He kicked her out and was stuck with the 6 kids.
I think that straight guys that don't like girl-girl action have been burned before in some way or another, or were close to someone who was burned.