Sure, Pacer is a little abbrasive, but The King himself seems like a cool guy who genuinely cares about the poor people of Freeside (Funny that an impersonator of Elvis, an icon of capitalism, would care about the poor. 
)
They let you be a "Lady King" if the player is female and their barber is, if not gay, extremely effeminate. So they seem like an accepting bunch. Plus they are friendly to The Followers of the Apocalypse, who seem to be good people.
I dunno, they give me comrade vibes.
The real Elvis was actually remarkably generous (though of course, a rich person giving away money to random people won't change the dynamics of capitalism)
As for the Kings from New Vegas, they do care about the community, but nothing more than that. A positive force for Freeside, but lacking any kind of broader scope - they do make for a good partner to the local branch of the followers of the Apocalypse though.
He was also a pedo though