While it does seem like this would give pre-existing selfish pools a competitive advantage (in addition to making the whole Bitcoin network less efficient), if you suppose that the selfish pool allows newcomers to join then it itself gains a sizable vulnerability- namely, that its advantaged position relies upon a secret (its extended block chain) that it must share with any potential collaborators.
An actor concerned with the viability of Bitcoin, in this scenario, would simply join the selfish pool and turn double-agent, broadcasting the selfish block chain. Assembling enough human Bitcoin operators to dominate the present-day Bitcoin network that way, and keeping such a rowdy band of idealists in line, sounds implausible.
I don't think that would work. Bitcoin miners only need a small header (the root of a hash tree, essentially) in order to mine, but you need the full contents of the block in order for it to be broadcast into the honest network.
An actor concerned with the viability of Bitcoin, in this scenario, would simply join the selfish pool and turn double-agent, broadcasting the selfish block chain. Assembling enough human Bitcoin operators to dominate the present-day Bitcoin network that way, and keeping such a rowdy band of idealists in line, sounds implausible.