Very poor public speaker. Can't handle opposition. Loses his cool under pressure. Definitely signs of early dementia. Acts like he never even thought of a counter to any of these reasonable questions. Responds with emotion when a better leader could defuse the situation with grace. Seems to be unacquainted with the normal tensions that can prevail when conflicting interests compete with different arguments. I would not even say Bernie Sanders is of average intelligence. He is of below-average intelligence and largely unable to articulate his own political agenda.
Just so you know. These melonheads are not supermen. Maybe they once were, thousands of years ago. Today they are inbred, watered-down, feebleminded simpletons often less intelligent than their Saps domesticated animals and almost universally inferior to their former warrior/sentry caste, the Neanderthals. When you have a fool for a leader it is because you are a fool. Saps should take his inferior shepherds and get the hell off the planet, neither of them belongs here. The next Ice Age should weigh in on this debate.
EDIT : One of the sweeping generalisations I have gathered from reading history is that there has never been a slave caste in recorded experience who has not fared much better than their masters in retaining intelligence, acumen, physical strength, agility, innovativeness and the instincts. The Greeks were doing fairly well when the Roman Empire fell (whatever happened to those people, they were replaced by immigrants into Greece today) and the Slavs retained much in the way of quality genes when they escaped their bondage. There are countless other examples. To use slave labor causes great degeneracy in the ruling class almost without exception. After 38,000+ years as a slave caste I reckon this is why the Neanderthals seemed to have emerged sharper than all the other races, some of them certainly smarter and more insightful originally than they are now. The Neanderthals have had to survive as journeymen and skilled labor this entire time, relying completely on their wits when others had circumstance of birth and inherited privileges. Always the outsider, the 'Thals have had to present something they offer that others cannot do and it has kept them keen.