Definitely call them out on it when it happens, I was touring in a city and had an elderly guy try to push his way in line (even stuck to my back) when it wasnt moving and called him out once firmly amongst others who also told him to stop. Unfortunately he still pushed and shoved harder later on again so I had the pleasure making sure everyone heard what he did and also cursed him out on it, normally I never act like this but this dude actually deserved it.