Nothing gets my blood boiling faster in public than some Veteran or fellow Service Member acting like an entitled Karen. Funny thing, almost all of them are peacetime never-deployed types or retired Officers and they're covered in veteran-themed clothing, or have a hat with their whole DD214 on it.
I really don't like getting involved with anyone else's crap in public, but there have been a few times I absolutely couldn't stand it and stepped in and pulled rank and/or corrected them accordingly.
How hard is it to ask 'Do you all still offer a military discount?' and if the answer is no, then no big freakin' deal. If the answer is yes, but.... with a lot of crap you don't want to deal with, that's your decision too and just pay the normal price with a smile.
Yelling at low-paid regular folks over the policies of a corporate mothership are a sign of not just being an asshole, but being an idiot as well. Similarly, you can tell a hell of a lot about a person by how they treat waitstaff and restaurant workers.