I can see Future Beans counseling Current Beans on having this attitude, but I find myself struggling to avoid rationalizing murder against these fools.
It brings me to a very good point I've seen written about "basic liberties" by Alan Dershowitz in regards to the public smoking ban arguments of 10 years ago. It goes like this: "Just as your right to swing your fist ends at the tip of my nose, so, too, does your right to puff on a cigarette ends at the edge of my nostrils." The hurtful things they do now could be so scarring to a family that making their protests illegal or cordoning off a 10-mile wide swath around the ceremony doesn't seem at all like a violation of their 1st amendment rights.
Here's another idea: set up a decoy funeral ceremony. Announce a completely bogus funeral location for the fallen servicemember, with the funeral detail and everything. Get stand-ins for the "family," and all the players. It could be legitimately played as funeral detail training, and while the WBC wackos protest your training, the real ceremony is going on miles away with the respect and dignity it deserves.