McCain's logic is that Libya could very well be the next Rwanda or Srebrenica -- and if it is, we really want to be non-neutral and on the right side of it. And yes, that's true, although unfortunately we don't have the luxury of knowing what the next Rwanda or Srebrenica is before it happens. Still, while creating a no-fly zone over Libya is a far cry from deploying 100,000 soldiers onto Libya's beaches, it's nonetheless an engagement. Robert Farley says it nicely:
Any decision to intervene means, effectively, that we have decided on regime change in Libya. This is to say that we’ve decided the rebels should win, and we’re willing to undertake steps that will make it easier for them to do so.
In other words, it would be very easy (and accurate) for Khaddafi to portray the struggle as one between him and the United States. I can't help thinking that that would make it easier, rather than harder, for him to retain his position of power. I get that not a lot of people like him, but a lot of people who don't like him hate us even more.
The usual caveats apply here: I'm no expert on foreign policy or on Libyan politics. Weight my views accordingly.