Magneto is probably a pretty good analogy for Byron, from a character motivation POV. They're both part of a minority group that *are* superior to humans and as a result have been persecuted for generations because of the very real threat they represent. I mean come on, a trained P12 can give you a stroke just by looking at you. They can crack your mind wide open, learn everything you know, wipe out and rebuild a personality from scratch, implant suggestions, false memory or doom a person to spend the rest of their life screaming at things only they can see. All without so much as laying a finger on them. There are even telekinetics, but they're very rare and most are unstable. If that's not superior, I don't know what is.
As a result, teeps have had some very very nasty things done to them, mostly by their own kind and mostly because the mundanes allowed or even encouraged them to do so. From birth or adolescence (depending on when they manifest) they've been rejected by "normal" human society, then betrayed and abused by Psi Corps which was supposed to be their surrogate family. Given all that, it's hardly surprising that the once that escaped are resentful towards mundanes to say the least.
As for a lack of gratitude; from where they sit, they've been used and abused by the likes of Sheridan (and indeed, Sheridan himself) so much that they quite rightly feel that they're *owed* allot more than they're being given.