This reminds me of something that happened to me in June. My best friend who considers himself gay, and refuses to identify himself as bi even though we had sex a few days after this scenario happened:
I had rented gay porn for my grad party, I got straight porn for my other friends because they are all grossed out by the latter. So before the grad party came around, my best friend(Cole) came by my house to preview the dvd, with his straight best friend(Jordan). Although his Jordan is completely straight, we all watched this gay porn. I personally would watch a gay porn vid before even considering straight stuff... straight just seems so fake to me, but two guys together is the hottest thing on the face of this earth. So I thought the video was good, but Cole had no immediate reaction, as I was watching him more than the video. Jordan kept giggling. I later found out from Cole that Jordan had "felt something" from the movie... Now I'm not an expert on the male brain by any means, but I could see Jordan being bi.
Now seeing as Cole had no reaction right away from the movie, I thought maybe he didn't like it. But I was to later find out, that it made him horny as hell, and it drove him to go hormones deep into sleeping with me. I should now mention I was drunk, so I didn't really think twice about it. But the context of him not reacting with a supposed straight Jordan around was odd to me? So to say that it depends strongly on where it happens and who is around is something I would say makes sence in my situation.