Never speak truth to power
Of course the BBC told people what they wanted to hear - to do otherwise has (historically) never been a good way to keep your head on your shoulders.
However the problem goes deeper. Whether Mark Thompson "lied" to parliament is a multi-layered question. Did he lie like a car salesperson does when he/she/it claims the car has only done 30,000 miles - while knowing full-well that it's done treble that mileage. Or did he lie like a computer manager lies - by simply not having a clue what he's talking about and being reliant on minions to feed him the truth (see above).
We all know that if you want to find the truth about an IT project (though, in reality few people ever want THAT much truth) you ask the programmers. I would suggest that if those people had been quizzed, either by the BBC trust or by the parliamentary committee they would have heard more truth than they could possibly deal with - and been told exactly how borked the project was - even when it had only been running a month or two.