The best way to stop this guy from doing more damage to others is to name names.

I see, that makes sense. 20k is pocket change when compared to the amount of damage that a tenant can do.

They would collect from the renters, AND they would then tell the owner they needed to repair damages for normal wear and charge them too.  

They will hire a local inspector to do the inspection and then issue you a policy that says if the inspector missed anything, you file a claim for damages with them and they will pay it.  

Look up https://www.irem.org/about-irem/member--amo-direct...Depending on area and how rough the tenant base will generally determine what rates companies charge.The rougher areas some charge 11 or 12% management fees because of low rent amounts and crime area with tough tenants you have to go collect on over and over and they tend to damage units a lot.Nicer more expensive properties in upscale areas some management might do 7% because rents are higher and tenants are less headache. 

Now the house is going through re-hab, no big damage, but all carpets and walls are very dirty.

This could be anything from termite damage to problems with the foundation to electrical wiring that is not up to code, etc.

It had extensive hail damage.

AND- can the land lord scream outside to passerby people, and neighbors that the tenant has damaged the apartment?  

In our experience (only 2 units, but over ten years) the worst of the worst tenants are those that made the choice to damage housing or not pay for housing when times got tough.