1) To be a neurosurgeon you need rather high mental capabilities, even more so if you're a very successful one. And being a neurosurgeon inevitably leads to quite some knowledge in psychology.
That does not make you knowledgeable in any relevant field for politics or leading the country.
2) He hasn't uttered any radical activist ideological crap like "I think when you spread the wealth around it's good for everybody" so far.
“You know Obamacare is really I think the worst thing that has happened in this nation since slavery. And it is in a way, it is slavery in a way, because it is making all of us subservient to the government, and it was never about health care. It was about control.”
"“Well, my thoughts are that marriage is between a man and a woman. It’s a well-established, fundamental pillar of society and no group, be they gays, be they NAMBLA, be they people who believe in bestiality. It doesn’t matter what they are. They don’t get to change the definition.”
"“There comes a time when people with values simply have to stand up. Think about Nazi Germany. Most of those people did not believe in what Hitler was doing. But did they speak up? Did they stand up for what they believe in? They did not, and you saw what happened.” (Referring to people voting for Obama)
"“I mean, [America is] very much like Nazi Germany. And I know you’re not supposed to say ‘Nazi Germany,’ but I don’t care about political correctness. You know, you had a government using its tools to intimidate the population. We now live in a society where people are afraid to say what they actually believe.”"
“Because 9/11 is an isolated incident. Things that are isolated issues as opposed to things that fundamentally change the United Sates of America and shift power from the people to the government. That is a huge shift. You have to take a long-term look at something that fundamentally changes the power structure of America.” (Claiming that ObamaCare is more damaging)
“Certainly there’s the potential because you have to recognize that we have a rapidly increasing national debt, a very unstable financial foundation, and you have all these things going on like the ISIS crisis that could very rapidly change things that are going on in our nation. And unless we begin to deal with these things in a comprehensive way and in a logical way there is no telling what could happen in just a couple of years.”" Claiming that Obama might impose martial law.
He is certainly a gifted neurosurgeon, I don't think anyone doubts that. But he is ignorant, he is radical, and he is utterly unqualified to hold the office of the presidency.