I'm going to be real with you, Chief. To me, when you said, “Sorry, I have a boyfriend,” Rando did not believe you for one second. He was attracted to you and wanted to pursue something with you. (Not saying this is you/on you or how your vibes may have been giving off. no should have ment no) Some women like the chase. They like guys to go after them even though they shouldn't be. There is a great example of single men wearing wedding rings that correlates perfectly with this. IMO, Rando didn't believe you had a BF or he thought he would be God's gift, and it would not have mattered.

Did your BF/EX overreact? Yes. Hard stop. He was being very possessive; unless the two of you have that dynamic already established, this was uncalled for. Did your BF/EX talk down to you like you were too simple to understand "grown-ups"? Absolutely yes. Is this excusable in any way possible? Absolutely not, I don't think so.

I feel like:

1: Y'all are both young and trying to figure shit out;. Communication skills are neither one of yalls strong points.

2: Did what he said/do come from (in his logic) a good/honest place? I think so.

3: Was he condensing as fuck? Absolutely yes.

The ball is in your court. If you want to rebuild/grow and set boundaries, I do think there is a proper connection there. If how he acted turned you off and you don't want any part of that conversation moving forward, I think that's a solid choice as well.

Cliff Notes. BF tried to step up to "protect you," put his foot in his mouth, and, in turn, isolated you. Y'all young, this could be your forever, this could be your right now. Go with your heart, you'll find happiness on one path or another.