That and the threat is world-wide threat, not just a US threat.
Keep in mind, I do freely admit that the guy is dickish.
Why is X-Force stepping over the line? I get why it's questionable, but I don't see how it's evil or anything. They went after genocidal monsters, like Selene, the Leper Queen, and Bastion. All of those people threatened the whole world, not just mutants. Besides, isn't it what Cap's SA team was meant to be? A team to go after threats proactively? They killed.
Also, I don't think anybody has given any candidates for leading mutants. And Scott has been training replacements. Dani Moonstar is one of them, and probably the biggest. And that's the whole point of the X-kids. Training the next generation.
So if you want to believe that Cyclops is going to turn evil and insane in the near future, you're free to do so, but just know that you have NO canonical evidence to support that.
My point is that if you define a character as good/evil based on evil=did not always do the right thing every single time, then I'll have to assume you're trolling.
Secret Avengers is a government sanctioned team that has used lethal force on missions. X-Force is a bunch of heroes who have decided to pro-actively go out and kill people they consider threats. There's a difference there.
I won't say something like X-Force isn't understandable.. but it's not the same thing as Secret Avengers. And even Scott knows it.