It's definitely true to an extent though. The slavers were definitely the worst of the worst type of people. I mean, there was not a decent one in the bunch. No one did it because that's just tradition, they did it because they were selfish and cruel. And it kind of looks to be the same way again. I've already whined about this before, but Caesar's legion still sounds completely unredeemable. I want to side with them, but 'taxation' will never be as bad as crucifiction, and I don't care what Ron Paul has to say about it.
They've actually stated that most people CL comes across are either enslaved or crucified. Maybe they're trying to unite the wasteland, but it's impossible to think of them as better than a republic that values individual rights and tolerance, no matter how corrupt it gets. (they cant be too corrupt if they're capable of being the winner in the end) There had best be a damn good reason to support Caesar if they want to keep claiming 'morally gray'.
Just because we help a faction, like NCR, to the end so that they "win", we still have no idea just what that will mean for the area. Even though we might help NCR take over the area around the strip, and/or the strip itself, it's very possible that the ending will have the area turn out worse or with its own unique set of problems as well as advances. This kind of thing is very much in line with Fallout where you would both have drawbacks and positive things about your actions.
I think the main thing that's holding us to believe CL to be basically pure "evil" is that we're applying our current-day mindset. But in a post-apoc wasteland, things work very differently. Not to mention, it's not only a post-apocalyptic wasteland, it's also a warzone. That's not to say the CL are not barbaric, the crucifying of enemies are a sign of that. But the way the world works (which we really should know if we read our history books and look at various wars) is that things are never black and white. Not even when they seem to be.
We don't know for sure, but I'm pretty confident that there'll be a point to CL besides being a "big bad".