Just to help out with my point...here is a question written in the on-line version of MensHealth magazine in the sex/relationships Q&A section...
Q:My girlfriend has extremely hot friends, and we're going on a beach trip. I'm worried about getting an erection. Is there anything I can do to control it? Digo, Miami, FL Sex Professor answers
It's best to have a multipronged approach: baggy swim trunks, dips in cool water, Jedi mind tricks (think about work), and a preregistered excuse: Tell your girlfriend you're worried about driftwood because you can't stop thinking about how hot she looks in a swimsuit.
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So in other words, the answer is basically "of course you will get an erection, because you would have sex with anyone who is remotely attractive to you, so just lie to your girlfriend and tell her the erection is about her, meanwhile, every man in the world who reads this knows that you will never have erections only for her".
Guys, can you try to imagine what this feels like to a woman reading it? We are basically being told that his being turned on by anyone and everyone shouldn't matter to us, because we women really dont matter to him. He wants sex with anyone. We individually are nothing special and no matter who you are or what you look like or how much he loves you, he will still want to have sex with all your hot girlfriends.
Again, I know this is over-simplifying. But this is a big problem within the world of men and women and trying to come to understanding about things.