I hate to be a buzzkill on the TSA bashing, but...
This IS the kind of thing that should get their attention! The apparent explosive of choice for these guys lately is PETN, which can be formed into different shapes or packed into various spaces. I say "Good on 'em" for seeing and examining the soap! It doesn't sound like they behaved poorly in the process either.
Out of curiosity, how often do you travel with the same amount/types of soap, and have they always let you through before?
While I agree the behavior is unusual enough that increased scrutiny is warranted, the TSO failed when he suggested a) the passenger ship it in the future, and b) that if he wanted to carry it through he should put it in his liquids zip-lock.