"A lot of people seem great until the wrong subject comes up" was basically the first line I wrote for this conversation.
I had a friend in junior high who strongly suspected I was gay on the simple basis that I wasn't homophobic. He never directly said it to me, but he said things that made it fairly obvious anyway, and there was tension. In high school, another friend confirmed that he thought I was gay.
Later in life, I had an epiphany similar to Susan's in Sister 3 in that I could find men attractive.
I never, ever want to talk about it with that person.
I know it's quite a bit different from Sam's situation, but it's definitely been on my mind while writing for him.