It does seem a little disrespectful when someone starts to deface any public property.  It is a disgrace and a lack of moral character when something like this happens.  No one in their right mind would think of doing this could it could land you in jail for starters.  Secondly, you could get sued and in today's litigious society you could go broke rather quick, even with a good lawyer.    I guess that's why we have laws.  Not only to protect the public, whether it be people or "spaces" because everyone is supposed to be allowed to enjoy the public domain.