It's not like we didn't have police, just not what we think of as a modern police force. We had organized law enforcement consisting of sheriffs and constables, with the power to deputize when needed.
This is much the same as we didn't have organized fire brigades, instead we had government officials with the power to organize a response to fires by recruiting more manpower from the populace to fight fires.
Asking if we need a police force because we didn't previously have one is like asking if we need a fire department because previously we only had an informal volunteer fire department. These things only worked in the past because the need was small enough that we didn't have the economy of scale to support a professional firefighting or police force, but with growth, the professionalization required necessitated the formation of these things.
Also the "cops are just slavecatchers" thing is a largely made up and exaggerated talking point by the far left that they repeat ad-nauseum. The first professional police forces in the US were formed in northern cities like Boston and were decidedly *NOT* slavecatchers, but rather organized out of groups normally deputized to enforce the law, turning them into professional employees -- in much the same way a volunteer fire department becomes a full time employer in cities that grow enough to need it.
Some early southern professional police and sheriff departments *were* constituted out of slave patrols, as these were people who were often deputized, but these were not the first police departments, nor did they constitute the majority of them, not even in the south.
