That depends. Are you treating the cats as retarded dependents, or as adult people?
My cat attacks solicitors, but not normal visitors or neighbors. Still trying to figure out how he knows who's who.
I don't treat them like people because they aren't, adult or otherwise.
I do treat them as independent contractors, if you will. I provide them a place to hang out (particularly in bad weather) and even provide some food in exchange for them cleaning out annoying rodents and the like from around our house. The mole population in our neighborhood is seriously endangered by my little hit squad. I insist, however, that they don't bring their work inside with them. That's one of my battles with them. I know they're often wanting to present me a trophy and I praise them for it, but outside the window, not inside.
I also try to mediate when they get into fights, mostly by asserting myself as the alpha male in the household. So far that works, but one of these days...