The capability of "curtailing" another race from expanding is contingent on having expanded into the galaxy.

It is contingent on having the physical capacity to have expanded, had they cared to.

Not going to curtail jack shit if you haven't left your homeworld. There's a large Universe out there, it's absurd to imagine muscling other races out without a wide-reaching presence, and that demands colonization.

So says the reflexive expansionist, too big for its britches, about to be taken down a peg via novas induced on the suns of its homeworlds by unidentified offended parties.

It is a dangerous galaxy, out there. Step carefully.

That is the dumbest thing I've ever read.