I don't ride on them.
The main reason I don't is because they are there for the thousands of families that have no grave side to go to. No fathers, mothers, daugters or sons to visit. With no bodies to bury; these memorials are the only places that they have to go to pay respect to there loved ones.
Think about it, If one of your family died at war and there bodies were never found wouldn't you want somewhere peaceful and respectful to remember them? I know I would. I'd want an untouched haven to go and commemorate these fallen men and the thought that the memorial was damaged in anyway would make me feel sick.
As other people have said, there are better places to ride. Some of you need to take a reality check.