Little Froggie,
I’m not being ‘Dan’ at all. A person has ‘nisyonos’ each different than the other,each person custom made to his/her own standing and circumstance. But case at hand – I know who I was looking at. It was no BT in any shape or form.
You say that you are not judging him, but by declaring that you know “who” you were looking at, you are judging him. And unless you know him personally, there is no way to tell whether he is a BT or not through clothing. I have met people dressed in a chassidish manner, complete with peyos, who just a year or two before were not yet frum. It happens, it really does. Maybe he wasn’t, who knows. The only reason I am responding with this possibility is that in your OP, you stated that you were bothered and shocked.