A Marine wouldn't insult an American citizen that supports them. You're a surrender monkey. We have Tea Party rallies with real Marines that mock stolen valor phonies like you.
How do you know that they are Marines? Because they have a shirt/hat/jacket on that says they are? That isn't really a good indicator, because some people like to wear them and pass themselves off as vets.
If you say it's because they were wearing their uniforms, I know you are lying, because it is illegal for ANY military member to show up at a political rally for one side or the other in uniform, as it will give the impression that that particular service supports a certain cause.
If you say it's because they were veterans and showed up in their old uniform, the above still applies. If you have been honorably discharged, you are allowed to wear your uniform, BUT, you must comply with all grooming standards, as well as comply with the regs concerning their wear (not going to political rallies).