I'm not part of the culture, so I don't understand it, but some guys just like hip hop, rap etc. and they kind of dress the part. Baggy jeans, a wifebeater and a 'do rag don't make a guy a "gangbanger".
Again, I never said he wore baggy pants or wore a wifebeater or whatever. You're making assumptions, and assuming I'm simply guessing based on his image. When you're living around gangbangers, you can spot them a mile away, and you can almost always tell when someone is just dressing the part as opposed to being an actual gang member. Just like how seasoned cops can usually tell if someone is up to no good, lying, etc.