Your friend is definitely the one in the wrong. I've been in that exact situation. My best friend introduced me to her new boyfriend and I fell in love with him immediately. We eventually went on a date and had sex. He left her the next day and we've been together ever since. She's still my best friend and was happy for us

It's to be expected in any monogamous society.

It's unfortunately about ownership. Which realy has no place in any society.

Your friend was trying to keep him for herself. Total selfish of her to even try since she didn't want a permanent relationship.

I don't think you deserve it but you should have expected it. It's just the way it goes when you go after your friend's ex as soon as they break up. It doesn't mean it's right that people think that but they do.

Oh the tangled webs we weave. I wonder how you would feel if you were in your best friend's position?

Yes.

I think the three of you out of just get together and go for it

You do not deserve hatred directed toward you.

You have to ask?

Yes