A philosopher would be the first to understand that no one is or can be excluded from the realm of ideas or thought.
Being a philosopher is not an extraordinary designation, such that it puts them beyond the mental abilities of someone of Elon's obvious mental aptitude.
Exclusion? Oh dear, here we go with the black or white. "realm of ideas or thought" - and the simplification. "not an extraordinary designation" - and dismissing philosophy. "beyond the mental abilities" - and more simplification. "mental aptitude" - you'll be fine then with neuroscientists or some such fixing the falcon.
It really doesn't matter who said it, it's just good to cite the source. But there is nothing which makes Michio Kaku infallible. Arguments can't be reliably evaluated according to who made them.
Like him or not, Elon Musk has an uncanny ability to figure things out. Of course he's wrong on some things, but for the most part, I wouldn't discount anything he says.
Being a philosopher is not an extraordinary designation, such that it puts them beyond the mental abilities of someone of Elon's obvious mental aptitude.