Maybe because it isn't about looking for the information at all. If one were simply curious, one could find out what one wanted to know and be satisfied.

I think therapists, especially the ones who terminate over this sort of thing, don't do it because their client has a human curiosity. They do it because when the client has to let them know that they know, it's a power grab, one with potentially dark undertones.

It's not really so much a 'confession' as it is a moment where the client makes the therapist feel vulnerable. Perhaps, even threatened. "You didn't tell me this, so I found out for myself and now I'm telling you I know, because I want you to know." And the undertone to that message is "I don't really care about treating you in a respectful, healthy manner. I care about myself and my feelings and I can justify anything I do as long as I really want to do it, so watch out."

People can do as they please, but if you google your therapists family and then tell them you've done it, I don't think you should be surprised if /when they terminate you. These aren't therapeutic boundaries, they're social ones.