Bonsoir,
1ère phrase: No one should deface walls
2ème phrase: Do you think these artists should stop drawing in cities just because mayors condemn street art?
3ème phrase: If they know the police can arrest them and judges will punish them severely, that should make them think twice about doing it again.
4ème phrase: How can street artists act more legally?
5ème phrase: Well, out of respect for residents, they could ask for permission first, at least.
Voilà, bonne soirée !