I love hooking up with people who are in a relationship
Why do you enjoy getting in between other's relationships?
It's just sex and it is better not to invest too much affection in one person.
Not wanting commitment in a relationship is fine, but you shouldn't sabotage other people's relationship due to your own beliefs. It's wrong to assume your way of thinking is the only right way.
Dude, I'm not sabotaging them. They are happy with my services.
You are sabotaging them by interfering with what they have. It is wrong to do that and if they are happy you shouldn't try to pursue them.