Ad hominem. Ad hominem is attack on the character of a person rather than his opinions or
arguments. The responder seems to disagree with Mr Calhoun for voting against the test and makes no argument for Calhoun's decisions, but rather, he attacks him. Even if he disagrees with Calhoun's opinions or arguments, he makes no valid argument why he thinks Mr Calhoun's stance makes no sense; instead, he goes at him "he isn't smart enough to pass the tests himself!" As I said, the responder seems to claim that Calhoun's objection occurred because he's not very smart, which is a personal attack and not for any other reasons.