I grew up in a different day, so this is probably less important now than it was then. In my time, guys had long hair, too. They also received a constant barrage of "Get a haircut, you look like a girl." Since your goal is passing as male, you need to remember that long hair leads people down the path of thinking you're female. People see what they see, and no amount of wanting on your end will change that. It shouldn't matter to you what others think, but you're indicating that it does matter to you, so your best bet is to be the most convincing dude you can be.
Hugs, Devlyn