He has his classic reasons, too. Aside from the fear of the unknown and the alien, at heart, he's obviously jealous and resentful that he has so much knowledge, but is still not the most powerful force.
Meanwhile he fears the nature of those with great power, which is revealed to be because of his childhood abuse, extrapolated into insecurites about those with power; the government, God, Superman, etc.
Yet despite that childhood abuse, he has spent a lifetime using knowledge to accrue power and then turning it on others, in essence becoming a bully and an abuser.
And so he recognizes this "Power corrupts" type flaw in himself, which is part of the reason why he has concerns about others with great power. It's a vicious cycle.
But he doesn't let that stop him from pursuit of ultimate knowledge, and even more power. In his own way, he's a very broken man.
What's cool is that they reveal it all backward, so you don't recognize how it's all layered together and relevant until the end.
It's interesting stuff.