[ozzymandus]

How does this idiot know what guns people own? Will she actually throw them out? Will she be sued for discrimination? Will people go to her greasy spoon, order the most expensive things on the menu, and then announce they own an AR and walk out?

[Blue Jays]

Exactly.

Order your food, ensure it is precisely as you want it, and only then remove your outer garment to reveal your AR-15 shirt before dining.

Commence eating. If they throw a hissy-fit and begin shouting, simply depart without paying.
If they hold their tongue, then pay with a credit card so they get whacked with the 4% service charge.
Tip the server very generously and advise them pro-gun people appreciate dedication and hard work.