Such a collection of junk would not be allowed at a National Cemetery.
You guys are harsh.
He is dead. You can be happy about that.
If the Academy grounds keeping crew is not up to your standards, tough.
Go read the obits and make sure you are not in them.
It is very common for things to be left on military headstones. Rocks, coins, and other things like cans of beer, ETC. Many things like this are left on graves at Arlington and even at the Vietnam Memorial Wall. The groundskeepers have designated times to gather the things left and certain things are kept and cataloged.
This is not unusual, and happens more often with recent deaths. I am not a McCain fan but this is part of military tradition.