One way to respond to vandalism is to use the following on the user's talk page:
[[Image:Banner_whose_side_are_you_on.png]]<br><br> Do you want to contribute good information, which will stay in articles and be read and enjoyed by many people over time?<br><br> Or do you want to add nonsense, which will be quickly reverted and soon forgotten?<br><br> Some of us have figured out which is more fun :-). Will you join us? ~~~~