How many irregulars are fighting in Libya on the rebel side? Quite a few, no doubt.
There were news stories a week or so ago (not sure of their veracity) of Gadhaffi shipping in Zimbabwean mercs. I suspect that story got wide circulation in Libya, given the technology of the modern day.
What you call paranoid strikes me as the world seen through the eyes of a comfortable Westerner in a safe country. When you go back to basic tribal behavior, which looks to be part of what is happening in Libya, a default is the mindset of "they" and "we" with continually narrowing definitions of "we" in operation. I'd offer Yugoslavia's break up, Rwanda, and Zimbabwe's efforts at the ethnic cleansing of whites as good examples of that mentality in operation.
It's a shame this happens, but it should not surprise you.
Rumor control and discipline are hard enough to maintain in organized units, where information is well vetted and spread. War brings out fear in people, with somewhat predictable outcomes.
It is also my observation that a civil war brings out the worst in people to a greater extent than other forms.
Consider what General Robert E Lee said after the battle of Fredericksburg:
It is well that war is so terrible - otherwise we would grow too fond of it.
I suspect that in time, once this rebellion is over, successful or otherwise, any number of people will have some deep regrets over what went down. They are caught in the moment and that moment is a war. Most of them are ill suited, and not trained, on how to handle it.