not op but violence is traditionally defined as physical force to cause harm. but now there's financial violence and social media violence and here the message in the graffiti causes harm. eg die techy scum. it's not physically violent, but some think it's helpful to frame it as a non-physical violent act because of the expression of dislike for a particular community. it doesn't cause any grave harm, but everyone who walks by and sees it is affected by it.
Violence has always extended beyond pure physical force. Calling someone a slur to their face, or spitting in their food, or defacing their clothes or home (especially with hateful symbols) would be recognized as forms of violence at many times in history way before modern times. Holding someone at knife or gun point is also very clearly a violent act.
