Lebanon is complicated. Don't believe anyone who claims that the current political instability is simply a matter of blah vs. blah. It's not.
If you want a concise overview, this Real News video is not bad. As is typical of Real News videos, it is far more balanced than most international events news reports.
Nevertheless, it makes the typical Western mistake of putting the word "sectarian" in the first sentence. Yes, most Shi'a certainly seem on the side of the opposition, and most Sunni on the side of the government. But it is arguably more realistic to view Lebanese political instability as a struggle between those who have effective representation in the national government (i.e., receive social services) and those who do not. (For a somewhat different interpretation that stresses the class nature of the conflict and sees Hezbollah as a throwback to sectarianism rather than a modernizing influence, see this interesting summary of Lebanese history.)
It is also arguably more realistic to view the instability as a competition between feudalism and modernity, but with some twists that Americans may have a hard time digesting. By "feudal," I mean a political system that remains under the control of traditional oligarchical families who effectively inherit power. They are no less feudal for having replaced war horses with Mercedes. The feudal forces, albeit with a modern capitalist veneer, are supported by the U.S. On the other side are the modernizers, but modernizers with an Islamic twist: it is arguably the case that the main road to political modernization in the Mideast is not the Western road of middle class democratization and civil rights but the road of what we might call "sectarian nationalism." In the case of Lebanon, it may be Shi'ite nationalism that will offer the successful alternative to continued control by traditional oligarchies. It is, after all, Hizbollah, that has the most modern political party in the country (i.e., a party structured bureaucratically and pursuing a platform rather than structured under a family and run for that family's benefit).
Think of the story as taking place in two concentric circles. The inner circle is Lebanese society, composed of groups of minorities that do not trust each other, or control each other, and that therefore are accustomed to cutting deals to prevent mutual destruction. The outer circle is the circling wolves of foreign interests fighting a proxy war at Lebanon's expense. Absent the outer circle, the Lebanese would probably find a compromise, but it is to the perceived, albeit short-term, benefit of numerous outside forces to persuade their Lebanese clients to take a hardline position. Hence, the mess.
Those Americans who sincerely think that "we are just trying to help" need to understand that there seems (to me, at least - I invite Lebanese to comment on this point) to be the following fundamental difference between Lebanese and American societies: Americans (still) trust each other (though it has lately been getting harder) and have confidence that their system is stronger than any individual leader, so they can (until fairly clear red lines like undermining the Supreme Court or arresting people without due process or presidential refusal to implement the law are crossed) accept a winner-take(almost)-all system. First, Americans don't expect gross violations of the rules; second, Americans assume that after 4 years, the other side will get another shot. In Lebanon, none of these assumptions holds, so no one can view with equanimity the prospect of letting the other side get effective control. Two different systems based on two different social realities.
The problem comes when outsiders try to impose a winner-take-all system on a society such as Lebanon's. Hardball politics in a system based on the rule of law is tolerable; hardball politics where leaders stand above the law gets people killed.