Felix, the counter to this is that there's no reason not to come up with the exact same class, change the flavor text, and call it something new. Which amounts, really, to the same thing.
I mean, my hypothetical chaotic-good assassin doesn't call himself a rogue7/assassin3. He calls himself a Peasant's Champion, the man who averts wars by going after evil, selfish nobles who are either warlike (which means "Lots of dead peasants") or abusive of their peasants (which, similarly, means "Lots of dead peasants"). He didn't kill anyone just for money, but he has killed a noble who was abusive and oppressive and planning a war against his neighbor that would have killed hundreds of peasants (as they were drafted unceremoniously into the infantry), and he did so in order to gain entry into the Order of the Peasant's Champions (that's me changing the flavor text of the quest requirement for the PrC).
There it is, folks: The Peasant's Champion. Do it exactly like the Assassin, mechanicswise, only take out "for money" and put in "only goes after nobles or people who prey upon peasants, servants, and weak social classes". Add appropriate flavor text for the different alignments, treating the peasant's relation with peasants as a druid's relationship with nature: "Good Peasant's Champions only target evil nobles who are directly hurting the peasants with their political aims or selfish desires, while Evil Peasant's Champions will happily kill any noble out of spite, provided that it does not cause retaliation against the populace. Good Peasant's Champions are offered hospitality by the people wherever they go, while Evil Peasant's Champions will manipulate or even sacrifice individual peasants in order to further their goals -- sacrificing a few for the benefit of the many, as it were. If a Peasant's Champion strays too far from his goal of protecting the peasants by levelling the playing field, however, his fellows will make an example of him. The only thing worse than a selfish noble is a Peasant's Champion who has sold out and lost sight of the cause..."