So what is the argument against Prop A? I found this site
that has an argument against it, which basically boils down to the GOP not wanting to give the Dems (who currently run the city) control over the police dept.
I'm not a Dem, but I am in favor of giving local municipalities control of their own police forces. Then, if the people of St Louis decide they're not doing a good job, they can vote them out of office.