I honestly have no problems with Damien, I don't really feel he did anything wrong.
Just seems weird to me to hate on him because he's a gay man struggling with his feelings so his relationship with Jasmine suffered.
The way the MC goes on about it, he acts like Damien was abusing her.
I see how you look at this, but I have a somewhat different opinion.
When MC and Damien meet, he offers to be his best friend, thereafter he only spies for another. Point 1 betrayal.
The second one is Damien (for quite some time Knows He's Gay, but still keeps his relationship with Jasmine.) and him having affairs with others.
The third one is Damien fighting inside the bowling hall, to prevent MC getting help...
So hating him is not the right thing, because MC (and me too) understand why he acted the way he did.
However, the trust he needs is completely gone.
And Damien wás abusing Jasmine, by having affairs.