Pointing and laughing is shaming.
So is throwing flowers.
Psychologically, screaming at them only hardens the resolve of the person behind the shield, the mask, the gun.
Shame, guilt, questioning what they are doing, that they are being used, that they will live with the shame for the rest of their lives...
Make fun of them. That tends to cut deeper. The protesters in Portland wearing costumes and playing music is demeaning to the troops. No reason to shoot at that, damnit!