I have a friend, he voted leave as it happens, when I said they told blatant lies his reaction was "Politicians always tell lies, that's life!". I just don't find that is acceptable. If a manifesto promise is made in good faith then cannot be delivered that is unfortunate. To lie about actual facts or bend reality is a different matter, that destroys faith in the individual(s). Boris has been so used to eloquently and convincingly telling lies that he now sees it as normal. Like Donald Trump he can no longer distinguish between inconvenient truth and convenient untruth. He has lost all trust for most of us, we have no idea what they are plotting over Brexit. If he has nothing positive to say then he will either say nothing or make up something which he thinks some of us may believe.
His inability to admit and more importantly learn from mistakes is even more damaging. He does not appear to know even when he is lying to himself.