Being in prison for an extended period of time would change even the best of us. In prison, the person sodomizing or receiving the oral sex is not gay, but the person being sodomized or giving the oral sex is considered gay. So, "that's the way it is there," seems like a logical answer and you shouldn't really mind. I'd look into the STDs and HIV more, like he said he would.
I'm sure that during the acts he didn't consider it gay, but more of another way to "get off." Plus it's hard to resist sex, in general. Also, I've heard many people say before "Gay sex is better than no sex," and that seems like the best answer for his actions. | 
