Nothing brings people together like a common enemy. You see this in schools all the time.
A group will decide one person is the āotherā (the āenemyā in this case) usually based on how that person, looks, speaks or acts, which is different to what they understand as the accepted norm. This is you, OP.
The group will then reinforce their own sense of belonging by harassing you. It draws a line between them and the other (you), making them feel like a distinguished member of a group and feeling that much coveted sense of belonging and purpose.
Iāve been on both sides of it in the past. When Iāve been on the group side, we didnāt physically hurt anyone but we did laugh at people. I didnāt recognise it as bullying at the time. I felt included and powerful. Itās very intoxicating. If youāve ever made a joke with a friend at someone elseās expense and both had a laugh, thatās an example of it. Even if youāre laughing at how some people are so bigoted and stupid, youāre still bonding in an āus v themā way, if you see what I mean. Itās natural and not fundamentally a bad thing but some people, partially children who havenāt been taught empathy, take it to its negative extreme.
Thereās mob mentality at play in your case too. Even the more empathetic kids will get caught up in the moment and behave in a way they wouldnāt do on their own.
Youāre dealing with several natural psychological and sociological phenomena here, OP. Itās a really difficult thing to fight against/protect yourself from.
My honest advice is for you to remove yourself from the situation. I donāt like saying that, because it means not doing something you enjoy doing and are entitled to do (street art), but thereās little you can do to stop horrible kids with horrible parents from abusing you. You are a very clear āotherā target in the way you look and act, and if you live in a certain type of area, which it sounds like you do, you just arenāt safe.