I witnessed a confrontation this morning at Walmart, but not over masks.
One of the suggestions that business are asked to follow (though most don't) is to have one-way dedicated entrances and exits. Walmart is doing this. If you're not familiar, they have two sets of big sliding doors, nominally marked entrance and exit, but they open into the same lobby area, so it doesn't really matter which one you go in/out of.
Walmart is now enforcing a strict in/out door policy. They've got barriers up dividing the lobby, barriers outside to direct the flow in and out , and a person outside to enforce it.
This morning, a man (no mask, natch) didn't feel like walking the extra 30 feet or so to go in the proper door, the woman outside stopped him, and he unloaded on her.
Nothing like seeing a 300-lb, 6'-5" man having a hissy fit in front of a much smaller middle-aged woman. Way to go, Cletus.
I hung around nearby in case I had to call the police, or run in and get help, but after all his bluster and mumbling over and over that he "can't believe this sh!t" he went in the proper way anyway. Jerk.