Okay I'm going to weigh in on the military issue (surprise surprise right?)

IMHO- They crash the welcome home musters because there is usually a group of brass present. They figure if the brass is there, they will hear what the 'people' are saying and heed their demands. The crashers also don't realize what a stress being in a war is on those soldiers and that there are very real consequences even for those who come home uninjured.