Dude,
I may not be the best PUA, but i know a little about Ethics
Right then, i'll put it this way:
A friend that disrespects you is not your friend. What I would do is move on and act like nothing happened, i would improve my game and steal a girl he is gaming, tit for tat, orr, i would just forget about it.... depending on how angry i was. He will get confused if you do the first option because, in the end, he stole your girl and you didn't respond at all to it, it will show him that you are the bigger man and that you don't care about a stupid thing like a girl. It is hard, but it all depends what foot you want to stand on, do you want to turn your back? do you want to stand and fight? or do you want to hug the guy, tell him he did well for stealing your girl and then move on and get an even better looking one?
Three choices.
I will leave it up to you
Love
G
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We are all equal.... Just some are more equal than others
Never settle for second place.