O_o
That's the reason you can't be evil?
Then play as a female?
Also, if you want to side with Powder Gangers it makes little sense to side with Legion as they oppose each other.
And Legion aren't evil.
And why are you doing a pure evil playthrough anyway?
Play as a cold-hearted bastard who's out to improve his own financial situation, and places money before most else, but he has a weak spot towards family because of the loss of his wife and son.
There, you can be evil, by siding with whoever holds the cash, and be good, by helping out those who remind you of the warmth a family can give.
There's no need to be pure evil, or rather; http://tvtropes.org/pmwiki/pmwiki.php/Main/StupidEvil.
It's an RPG, create a character who has his/her bad sides and his/her good sides.
But don't go "Oh I'm gonna be evil for the sake of being evil!" and side with Legion because of it.
[edit]
Waitwaitwaitwait...
If they end up looking like John Wayne, whoever the hell that is, then make a korean character? A black character? Hispanic? How about a goth? Or a punk rocker? Create one that looks so ugly only a mother can love him?