Why did the U.S. and NATO feel it was necessary to intervene?

Geez your an idiot if your usin that logic than how come they intervened in Somila?....different polotical aspects in Bosina they intervened to stop the rebeals from over throwing the gov't.....in Serbia it was to help garentee the independance of a new nation with out back lach from another....Kuwait was to stop Iraq from tacking over....in all of these cases they intervened to help the gov'ts keep power in the cases of Rhawanda and Leone the gov't have no problems kepping power and they do not want help from NATO