Magnus is obviously extremely qualified to detect cheating, I see many other people who are honestly just as qualified as him say that Hans isn't cheating. I'm going to also say emotions are going to play a massive role here, both in terms of defence of Hans and against Hans.
The interesting thing is the one party MORE qualified than Magnus and the other grandmasters to detect cheating is the chesscom statistics team and they think Hans has cheated online recently and didn't admit to it. Still, there's no smoking gun that proves the OTB matches were fixed, Hans can be innocent at least in those specific circumstances, but if he's been guilty in online chess recently is it truly fair to make the world champion play against him OTB?
>He wouldn't risk his whole reputation for nothing.
It is pretty important to realise in terms of Magnus's mindset he has given up on defending the world championship and doing anything other than achieving 2900 elo, the highest rating ever achieved. He is a champion, and that is his goal in life, he wants that rating in a way most people can't fathom. If he proves Hans Neimann is a cheater, Han's win's against Magnus are void, and Magnus's rating goes up. Imagine being the world champion and having your dream drift further away because of a known cheater beating you when they're at a disadvantage, what goes through your head? What goes through your head when you think of how many people COULD be cheating and making getting 2900 impossible? What can others do about the spectre of chess cheating, the world champion, doesn't stand up?
So what I'm saying here is, I wouldn't be super confident that Magnus wouldn't throw his reputation in the trash to become the greatest chess player who ever lived. I think he would absolutely throw away his reputation, but not for nothing.