dreams -sexual- tendency

One day I accidentally had a very graphic and sexually explicit dream with a person I used to work with and to whom I didn't feel remotely attracted to. Why my subconscious chose him instead of, say, Amanda Palmer still remains a mystery to me.

I made the comment to my flatmate during breakfast. For the coming weeks, at work, I couldn't look at him in the eyes without picturing him naked and feeling somehow guilty and attracted at the same time, and that was creepy.
According to my flatmate's pseudo-Freudian interpretation of dreams if you have sex with someone in dreams it meant we would be friends forever. I didn't even know him or had anything close to friendship with him.

Again, my subconscious never chooses the friends I love most to have dreams with graphical sexual content with. I do dream sometimes of close friends and kiss, hug or get closer to them in an unusual affective way, but I don't think my subconscious would ever choose to have explicit sexual scenes with them, no matter how forever I am going to be friends with them.

I have had wet dreams with girls, strangers, but never with animals for instance (no matter how much I love them), close friends or family members or... my gay flatmate.
So, sexual tendency and sexual ethics still remain, even unconscious?
Interesting brain we have... What did that mean, then? Why him? Why was I condemned to see him in the office and blush?

I came up with some answers. Basically, I think that my subconscious needed to make up for bad sex with a particular someone I was physically attracted to and chose a random person I never looked at sexually but who I shouldn't feel intimidated with so I could use him as a scape valve.
An onyric way to turn things around from being attracted to someone, but not satisfied, to the exact opposite: being satisfied by someone, but not attracted to.
It has a touch of sad. I didn't think the latter could be possible. But you always learn...