Hi Lone_Twin4,
I think its a shame that your friends are being so childish. Dating is about your affection for one another, not about whether or not you were friends with his ex. If they were good friends they would be supportive of you having a relationship that makes you happy, no matter who's ex it is. Furthermore you aren't friends with this ex anymore so the friend's don't date friend's exes rule doesn't apply here, in my opinion.
Shouldn't the LGBT understand that Bisexuals also date men? I'm straight and I understand the concept of Bisexual. O_o Its not a matter of it being a phase if you're openly, accepting Bisexual, its a matter of you finding companionship with one of your sexualities.
Be strong girl, you deserve happiness and your friends are just being childish.