In fact, it happened to me just last week at BWI. GA made a fairly public scene about my carry-on because it was a CRJ with no room. I was at front of Z1 line so I guess the first target. She said "sir, there is no way that bag will fit on this aircraft. You have to check your bag!" and let out an incredibly audible and obvious huff/sigh.

I would like to think I wasn't a complete jerk when I said "I'm aware, that's why I have this sky-check tag right here..." I probably was though. She ticked me off.

I have visible SE tags and was in the Z1/2 line waiting to board an aircraft without a J section so it's clear at that point I have status whether the tags are visible or not. So if they can/do talk to us dime-a-dozens that way...

In fairness, she may well have spoken to each and every passenger that way. I wouldn't know because I boarded first.

On an unrelated note, it sucks that we don't just believe one another as a default until given reason not to trust someone. Seems like a strange thing to make up. To what end??