You have to look at it in context to there future goals. They used the Slavers yes, and the crime families for good reasons.
Please elaborate.
Ever power in the wasteland is guilty of mass murder.
Neither the Brotherhood of Steel nor New California Republic ever committed mass murder to my knowledge, and this is to say nothing of the governing bodies of single settlements which tend to just want to get by. The only exception would likely be Raider settlements and New Reno.
Genocide is the only acceptable answer to safely eliminate all the dangers in the wastes in the least resource draining way.
All dangers except the biggest of all: the Enclave.
Genocide is
never an acceptable answer,
ever. What gives you the right to play god and decide who lives and who dies? What gives you the right to determine what will or will not make the world a better place? The Enclave doesn't even know the long term consequences of their goals; they're just as ignorant as everyone else about the future. Not once did they think about what effect their poisonous strands of FEV would have on the environment, and future generations. No one can foresee what will happen in a few years, let alone a few centuries.
There "elitist group" as you say was the reminder of "humanity".
Wastelanders are human too. So because they have a few strands of modified DNA wastelanders are mutants who are undeserving of life?
There two goals are to make the wasteland safe, and rebuild the country. Both goals are "good" just how they go about doing that is the "evil" 2 goods and one evil I would say make a "gray".
No their motivation is made quite clear in Fallout 2: power. America is dead, and the world the Enclave would "rebuild" wouldn't resemble the United States at all. Ever seen a fascist dictatorship up close and personal? That's what the Enclave resembles, and that's ultimately what would become the "new America".
IIRC Richardson said something to the effect of "Sorry it has to be this way but but we have no choice, i'm sorry" to you when talking about the FEV
I have no doubt that Richardson actually believed what he was saying, but so do all madmen.