I feel very strongly about this issue. As I've just been chipped by Scratchie in another thread for voicing my opinion , I choose my words carefully. So here go's. If you don't have the fortitude to speak up then your part of the problem. These people do this because most turn a blind eye . Confront them , make them feel uncomfortable. I commend you for wanting to do something , but the offender is long gone and the damage has been done. Voice your opinion then and there, then report it to the authoritys. Think of this, you spot a small fire , your capable of putting it out, you don't, you leave and call for help. Fire brigade arrives but it's to late, its out of control. You, as a member of society have the authority to speak up. Try it, you will feel better for it.