It seems entirely appropriate to me that Greg Dyke has had to resign as Director General of the BBC. Whenever an organization goes against its own stated objectives, the head of the organization usually pays the price.
On its web site, the BBC states, "The BBC is explicitly forbidden from broadcasting its own opinions on current affairs or matters of public policy, except broadcasting issues". When Andrew Gilligan made his famous "sexed up" statement he was clearly adding his own opinion when he said that the government "probably knew" the intelligence was wrong. He allowed his own opinions to influence his reporting.
However, that broadcast was not Mr. Dyke's fault. If a proper control system were in place, Mr. Gilligan's controversial assertions would have been tested and confirmed or otherwise. It is that system - controls - that ultimately cost Mr. Dyke his job. A proper controls system would have seen the BBC retract or rephrase that statement in a manner that was closer to the truth.
I don't actually believe it is possible to be "impartial" nor is it desirable. The real lesson from this is that the media should not be so close to the government. The government controls the purse strings of the BBC (same with RTE and the Irish government) and the BBC is accountable to the government. This fiasco shows that there should be no government funded or provided radio or television service. It is unnecessary.