I don't view it as character assassination so much as suspicion by association. He was part of the group (Bush + Obama Administrations) that pushed for these programs. It makes him more suspect to be lying than a random person. It's not proof of a lie, just reason for scepticism (grain of salt and all that).

The stuff about Snowden doesn't even make any sense. The fact that he's a high school drop-out doesn't matter. Some people who drop out of high school have a lower intelligence, but that doesn't imply the Snowden does. The fact that he worked for the CIA, the NSA, and as a NSA contractor actually implies that he is either intelligent or the CIA/NSA are incompetent. Even if Snowden was of lower intelligence, it would imply that there is less likelihood that the documents are elaborate fakes, and more likely to the be the real deal.

I was just bringing the point to light for discussion.