Certainly if they're like us, and travelling to new worlds, they'll be imperialistic and colonial. They'll plant a flag, because we obviously weren't really making use of the planet, not _really_, and attempt to civilise the natives through something between cultural erasure and genocide.
On Earth, in the grand scheme of things, it took a very short time for colonies to a) diverge politically or b) fail. It's not something that stopped happening (much) because we became more cuddly. It's just boring old economics.
So I think it's unfeasible to maintain a society that rules with an iron fist over interstellar distance and time.
