More think he should be impeached if he goes to war with Syria despite a No vote from Congress and despite UN saying no, and breaking international law. I think the NSA thing is at least as big as that, and if he does both then it's that much clearer that he's acting as a dictator with unlimited powers that needs to be overthrown.
He has no regard for the Constitution, no regard for human rights, no regard for due process, and no regard for international law. Not doing it would just send a message to other psychopaths running for president the next time, that it's okay to blatantly lie to the electorate, and then do stuff at least as bad as he did. Impeach him.