This is a tough one my friend.  I have had this turn out 3 different way with 3 different str8 dudes in my life.

1.  I told one of them an he just went balls out ballistic.  I grew up and became an adult in the early 80s during the time that HIV/AIDS first came around.  He accused me of trying to sleep with him just because I wanted to give him AIDS.  Absolute nightmare.  I could never forgive him for it.

2.  I had this dude tell me that if we were going to remain friends we would deal.  However, if we were going to bring it up everyday then he said that he would rather end the friendship.  There was never an issue before and he didn't want it now either.

3.  I told him and it shocked him at first but hugged me and said that nothing would change the way he felt about me and it didn't.  In fact we dated in high school and I was the one that who ended it because he really was Str8 and I knew that I risked ruin his life if he went forward with me.  He was born str8.