Large maglight-style flashlights like that were often carried by people who weren't permitted to carry a truncheon/nightstick, as a big stick full of D cell batteries is an extremely effective club (until it bends). While the idea that mostly people who owned them used them to beat black people is a bit hyperbolic (for a long time they were just the most reliable flashlight you could get) they definitely were also used as a bludgeon. Mostly that role has now been filled by telescoping batons though, just as effective but much less weight to carry around.