They don't choose people or seek out their victims because of their sexual orientation, or race, religion or disability according to recent reports. Bullies seek out their prey mainly because their easy targets. Once they find their target then the bully seeks out qualities of the victim to pick on. Let's use Joe and Manny for example:: Joe the bully is an angry person who maybe learn his aggressions from home. Maybe he witnesses domestic violence between his mother and father. He becomes mad at the world, he wants to feel powerful and strong. He targets Manny, because Manny may be shy, or displays vulnerability, or lacks self confidence. Maybe Manny has few friends, no one to stick up for him. So Joe targets and starts to bully Manny. But Joe has to figure out his game plan of attack, what is it about Manny that Joe can bully. Let's say for argument sake that Manny is openly gay, he is effeminate in his speech, and talks softly. Joe has found his niche in Manny. So Joe begins his rant by calling Manny gay slurs, pushes Manny down, trips Manny, takes Manny's books, etc., Joe has started a bullying crusade against Manny and the bullying theme targets the fact that Manny is gay in in conjunction with all the attributes that are personal to Manny. Manny now becomes the perfect target. Bullies seek out prey that are easy to bully, bottom line.
Let's be clear though, most victims do not actively provoke their tormentors. Their helplessness does it for them, according to recent articles.