It's often freaky to see or hear from an ex. Brings up all kinds of memories. Good and bad. Maybe you should reassure your Bear of how much he means to you?
Plain as that. It goes back to those primordial urges. If this new guy really cares about you, those types of confrontations can really sting.
It would definately be worth talking over with him outside of the haze of smoke and tump of base. Not in an accusatory way but just to discuss what type of feelings you were both having.
One question though. Why didn't you just say, "ok, this is too weird," and head for another club? Did you perhaps enjoy the attention you were obviously noticing from your ex?
Sometimes we only have to look at our own behaviour to understand why someone else would be hurt.
Mabe everytime you was glancing at your EX, your bear was glancing at you!
Then you told him that the guy was your EX?
Oooo, i'd say he got pissed.
Was you drunk enough to not notice him noticing you?
Might be a problem!
He might be thinking your lusting after someone from your past and that would mean he thinks that you enjoyed the EX better.
Hope this helps you see his view.
If i was in public with my woman drinking, i would be noticing stuff like that.
Just a jelous guys point of view.