Ed T, comparing a comedian/shock jock like Don Imus to a distinguished journalist is hardly a fair comparison. And beyond that, Imus, whose stock-in-trade is/was outrageous gags and pranks and commentary, was "fired" numerous times but always seemed to have yet another of his 9 lives intact.   Same goes for people like Rush Limbaugh whose deliberately OTT and politically incorrect shtick sometimes gets them bounced from one gig, only to pop up again Wack-A-Mole-like in another.   
Helen Thomas's situation is one where, aside from G W Bush having basically kicked her to the curb early in his administration for actually doing what the press is supposed to do, she has had a stellar and most responsible career for decades.