The OP's troll-esque attitude aside, the real problem with immunity to sneak attack is that it singles out a specific class. Would a monster that was 'immune to rangers' be fair? No. Yet apparently some folks think it's fine that every other monster is immune to sneak attacks, the rogue's most useful ability in combat.
Worse yet, there's no logical reason that undead have to work this way. Why zombies would be the absolute bane of sneaky types is beyond me.
Monsters should only have immunities to damage types that are shared across classes. Either that, or they should start handing out 'immune to bare-handed attacks', 'immune to arrows and animals', and 'immune to magic missile' to balance things out.
"Sorry bard! This kobold is immune to catchy tunes! You're useless! Better luck next campaign."
Care to rephrase the troll apart again? Calling someone a troll or showing troll like behaviour is the same thing. I don't call you any names and I would appreciate it if you didn't call me names either. If you can't control yourself please seek another thread.
Anyway, the problem is relying too heavily on SA and thinking that is all that makes you useful.