I missed this earlier. This is not true, because police forces, as well as private security forces, do not work for free, and will support whoever is paying their paychecks. In that scenario, it will be the people with the wealth, not the rioters who are rioting due to lack of it.
You must read more carefully - I wrote
large part, not the police entirely. Of course there will be bastards who will shot rioters, but another part will support them. Looking here in Europe, I can give you some examples of police strikes against their own layoffs, wage cuts etc. It will be the same as in any other civil war - paying money doesn't means that people will fight on your side!