Frankly, I enjoy even the pain... gradually melting into an oblivious blur of bliss. It shuts off my mind and I become nothing but the feeling of being wrapped around a violently thrusting cock.
And, no... its not just a gay thing... I like it even better when its a hot woman pegging me with a fat strap on,
And as to the question of the psychology, in taking it, orally or anally without reciprocity... being dominated surely plays into it. I have been dominant in relationships and been dominated... and both forms of sexual theater are wonderfully stimulating.
But the best is when the person you're with is particularly energized and aroused by the role they are playing... then it just becomes a feedback loop of escalating excitement.
A woman or a man, who really gets off on dominating me, turns me into their absolute bitch... and when my partner totally dives into the pain and humiliation of being dominated, it turns me into a sexual sadist of the first order.
( by the same token... I also enjoy when lovemaking is gentle, caressing, and restorative... as long as that is the mood of my partner.... the variety of it all helps keep the passion burning )