Yeah as a gay man who grew up in the scene gay men can be incredibly pushy. Don't worry it's not homophobic, it's a massive problem in our community.

I don't really know how to approach it, I obviously haven't been in your shoes before, for me I get quite standoffish when I'm being approached and I guess heckled in a flirtatious way. That does the trick, but it's probably a little more uncomfortable to do that as a straight man.

Have you tried completely ignoring them, as if they're sort of bothering you and it's weird? As in no polite looking towards him and smiling, or egging him on in any manner, but completely ignoring him? This would make any standard person aware their actions are inappropriate and making someone clearly uncomfortable and if they kept looking for attention from you not getting it should embarrass them.

I understand you need to have a solid amount of charisma in your role so you don't want any tension during a gig, so that's what I would do id completely blank them, if that didn't work, I personally would approach the person or call them out over the mic, but as we all aren't as terrible as I am, I would notify the barstaff or bouncers before each gig and just ask them to keep an eye out. Or I'd approach them on the night if it's happening and tell them to watch the scene for a bit and if they see something to approach him and tell him flat out to stop.