Supreme court doesn't have a leg to stand on, and they are well aware.
What must happen, under American law is
Protestors tell officials about the protest
The Fuzz turn up
If people are protesting legitimately, then the police do nothing
If the protesters are aggressive or extremely disorderly, or if they commit defamation/libel, or any personal insults at the soldier that are sufficient to count as abuse, then they take action.
Actually, one of the things is/potentially isagainst the law
A sign saying "You are a war criminal" certainly counts as makes a claim, expressly stated or implied to be factual, that may give an individual, business, product,group, government, or nation a negative image. It is usually a requirement that this claim be false and that the publication is communicated to someone other than the person defamed.
Also, they are jerks :P
