I think I heard them doing more graffiti on my fence just now. I could hear the spray cans being shaken.
I considered going out there or yelling to them to eff off from this side of the fence but I decided that no good could come from it and if I antagonised them then they might retaliate against me or my house in the future.
Just have to let them do it. Watched them ride off out the window. Two individuals on bikes.