Trump should have pardoned him. Even if morally guilty of anything, he's suffered a great deal already, and blowing the whistle on our corrupt gov, which Trump should already understand exists, is a service, not a crime.
If anyone is looking for a bad mark on Trump, this is one.
I don't think it's appropriate or accurate to think there are only 2 sides. The world is full of people who have their own interests and they will exploit each other for their own gain. The Deep State Swamp doesn't like Trump. Trump is a smart guy in many ways, but in others, he's very naive. Trump is a proud American, and foolishly trustworthy of the beast that hates him. Trump doesn't like Assange because Assange embarrassed the US military.