Pro-police forces WANT mayhem. It makes people watching on TV afraid of the protests, and it changes the subject away from the widespread peaceful opposition to racist police violence.
Claiming "pro-police forces WANT mayhem" paints the situation in a very generalized, unhelpful, us-versus-them light.
There are definitely some pro-police forces that probably want some mayhem, for exactly the reason you state. There's probably others that want mayhem for other reasons. Across the board, however, I'd imagine most pro-police groups of people prefer peaceful protests that don't put officer lives at risk, not to mention all the collateral damage to protestors, buildings, economies, etc. that also could be avoided.
It's entirely possible (and, I'd argue, likely) that pro-police people aren't some homogenous group of schemers. You can be enraged about police brutality, abuse, and misconduct -- and also enraged by violent riots.
They're either murderous or have "lucky" bad aim.
Exceptions apply for swat snipers in hostage situation
Which is the whole point of the protests. If an officer is on a riot line and is murderous but the other officers on the line don't take them out (send them home or prosecute them), then the officers are just selectively enforcing the law (which I realize is a concept in US law enforcement) to the point of being corrupt.