So... let me get this straight.
You asked someone out. She said some variety of "no." You kept pursuing, then found out that she liked someone else and broke off the chase.
She is now angry that you broke off.
You apologized and offered to be a gentleman (what does this mean? And why does it matter?).
She says no.
You listen to her.
Now your male friends are saying you're weak because you listened to what she said, and you're wondering if they're right.
My dear friend, no means no and as someone with intimate knowledge of how girly social circles work it's better to be seen as that girl's bitch than as a potential rapist. The former information might get you laughed at in her little friend group, but the latter information travels widely through gossip channels and gets people blacklisted.
Being a gentleman is not something you do "in order to be nice," as though it's a reward for good behavior. A gentleman just Is. The fact that you ignored her "no" in the first place was wrong of you. It sounds like you could use an update to your communication skills and could work on boundary-setting, because you indeed shouldn't let that girl twist you around her finger after you already decided you weren't interested (she needs to learn to listen to your "no"). Some listening skills might also be in order, since the story as you've related it doesn't make a lot of sense to me (what is going on with that girl's emotional reactions?).
It sounds like you managed to do the sensible thing at the end. You may tell your friend to go fuck himself or instigate a round of fisticuffs, though I'd just ignore him. Listening to women doesn't make you unmanly. And even if you were, in general, on the more passive and nurturing side, there's plenty of people (including female people) who prefer that.