Ugh, yeah hairdressers can be far too judgmental or conservative sometimes. I had a hell of a time just finding someone who'd cut my undercut like I wanted, rather than trying to make it "more feminine" than I'd asked for. Even when I went to a barber's called Fellaz, they eventually tried to make it feminine.

Maybe find a picture of the kind of thing you'd like, and go in with that to show them? It might help you convince them that you do know what you're talking about and you do really want it like this.