YouTube would basically screw themselves over and guarantee their demise if they did this, for many reasons.
For starters, YouTube makes a lot of money off of Pewdiepie. To take away his monetization would not only take away his revenue stream, but theirs as well. Estimations put that amount of money at over $100,000 monthly.
Secondly, it could drive Pewdiepie off of the platform. Pewdiepie does make a lot of his money through means outside of just YouTube revenue, but it’s still a large enough source of income that Pewdiepie might choose to move to another platform like Dailymotion, Vimeo, or Amazon Video Direct, which all have monetization schemes as well. Any of those sites would kill to have Pewdiepie and his 50+ million fans, and that could create a serious competitor to YouTube.
Lastly, this would signal to many other creators that YouTube is not on their side. Large YouTubers who post controversial content like H3H3, Philip Defranco, RiceGum, LeafyisHere, and many more would likely make plans to ditch the platform for one that has more security.