I lived in roxborough in philly until I was in 6th grade, I remember one of my friends older brother went over a couple gang tags. They found him going over a throwie and beat the shit out of him. not smart to go over gang tags unless you know who your dealing with.
I make a point to hit over gang shit. Fuck those guys. Graffiti is about love and respect for the world around you. Fucking gangbangers use it to mark territory and spread fear.
I went over this Toy in my neighborhood. His shit is whack and nobody knows who he is. I wouldn't go over gang shit because its extra drama you don't need when you just wanna paint. I don't paint to Vandalize anything. I don't go on people's houses or property, schools, places of worship nothing like that its corny. A few losers in my neighborhood do. Makes it worse for us. But if I could give any advise do whatever you wanna do just be prepared for the consequences of it. Somebody might crack your head open for something even more meaningless anyway so do what you wanna do. Just don't be surprised if you get slapped around a little haha.