In a democratic society, if citizens are particularly concerned about the aesthetics of public property, they can make their views known to the relevant authorities and elected representatives, and it could even become an election issue. I think that's far better than citizens fighting with paint.
Broken window theory. Once a few things have graffiti, it will quickly proliferate including stuff that isn't exactly aesthetic.
Any cursory googling will yield several papers debunking the broken window theory for you.
Sorry, I used the term incorrectly. I'm not suggesting that graffiti increases crime, only that the presence of graffiti encourages more graffiti.
I live in Japan which is usually free of litter, put a few empty beer cans on the floor and come back 24 hours after and you will have a trash pile. I don't need a paper to tell me that.
I see no problem with this, if someone graffitis public trains or a park bench there's zero need to paint them over. Some karen in the municipality decided a bench should be painted green or a roundabout have some weird sculpture, but a random citizen can't paint some tag on a light pole? Give me a break. It's not like there's some holy committee of aesthetics at your local council.
Citizens can even "fight among each other" by painting it over when they dislike what was there before. It has no downsides on functionality, if anything the extra paint coatings protect the public objects more from the elements.