Such people are beneath contempt.

Were I there, I would have slapped the egg from the guy's mouth and told him to get himself and his raggedy mutts out of there. A burial mound, cemetery, grave site, etc etc...is a place to show the utmost respect. Esp. when they contain the fallen of battle.

My grandfathers and uncles served in WW2 and if someone set up a picnic on their grave...well, they won't have far to travel after I am done with them.

Certainly a park warden or a member of some society or club could monitor the site to keep such morons from acting in such a foolish way.