Even if it were, rebelling against such a terrible person/robot/whatever would be its own reward.
Isn't Roko's Basilisk just god reflected? Determining a moral debt. Testing it's creations (facsimiles of it's perception of 'itself' imbued upon human beings) who had no say in it's creation? I do however agree that 'rebelling' against a terrible whatever is it's own reward!
I'd argue that having created the universe and everything in it is a morally significant difference, but, yeah, that's an admittedly really easy conclusion to come to if one doesn't share that presupposition.
ETA: To clarify, the thing that makes Roko's Basilisk so horrible is that unlike God its existence doesn't precede and can't possibly be said to have any epistemic or hermeneutical priority over that of moral facts (also that eternal torture is
inherently horrible and I follow the Cappadocian Fathers in sincerely hoping that the actual God doesn't actually do that). Obviously a humanist morality wouldn't consider this a relevant difference and I wouldn't expect it to.