For a long time he thought the moon landing was fake. That's not a position you arrive at with reasoned science and understanding how the world works. He's stated he thinks Bigfoot could be real. He does the same thing on a myriad of other topics. He presents some random quack as just as valid as real science.
If he was just some random dude none of this would matter. But with 11 million followers, sometimes this "my youtube research is just as valid as your scientific research" attitude can do real harm, as it did with vaccines.