When you want to harass someone - and let's be honest, you, dear reader, have indeed wanted to harass someone at some point in your life - what do you do? You pick something you believe they will be sensitive to and remind them of it in a mean-spirited way. So, if the bully can tell you're a girl in a male-dominated space, that's what he's going to pick. You may (and problably do) receive this as worse harassment than I receive being called a faggot ("Lol another guy calling me a faggot"), but the bully doesn't need to be a worse person in order to choose to harass you in that way. Both times, it's the exact same guy, and both times, he's just reaching into his insult grab bag. What's he's not doing (necessarily, anyways) by calling you a "stupid slut" is revealing his deep-seated mistrust of women. If you're coming to that conclusion, you're overrating the complexity of the thought process that goes into online harassment. Which is to say, the problem is not what he thinks - it's that he's not.