I relate! When triggered, I shake terribly. I've even had the perpetrator himself stop, do a double-take, and say in amazement, "You're shaking!"
Ok. Now try to relate to shaking, can't walk, your service dog is alerting you (and I ALWAYS thank my SD in training for alerting me as it always has to be a good thing) so stop to do that, have to some how get him and I through the store to at least the door.
I am training my SD in training to find the nearest exit for this reason. This and disocossation.
And remember, I have me, my purse, the leash, my service dog that I must keep in command, my stuff i am trying to buy, fumbling with my wallet. And other things.
All because someone wanted to confront me that I don't need a service dog or even reaching for him, which makes me freak due to reaching also for me, and then he is now focused on them and I have to spend 30 mins getting him back focused on me. So i went to go get milk and toliet paper and spend an hour in there due to someone's ignorance.
ETA: And for something like a sezuire alert dog, they can miss a sezuire alert due to this which can be life threatening.
Any way you turn it, it isn't good.
ETA: I want to add even if someone asks and doesn't reach for him, that is very anxiety driven as I am terrifed of people. So even that can cause all of the above and more.
I don't mind a quick 1 or 2 liner education but NO ONE is happy with that it seems and they seem to carry it on and on and on when all I want to do is shop like a normal person. Go to the mall like a normal person. Ride a bus or the train like a normal person. Go to a park like a normal person. Etc.