Too many people were only too eager to swallow the narrative SYP fed them, because it was the easiest one to take. In Thatcher's Britain, the police were little more than a private army, and could do no wrong.
Ingham was never going to change his mind, as he saw himself as Thatcher's sword and shield, defender of her legacy. Any attack on the police was an attack on That Woman, that abhorrent woman.
You could lay all the evidence to the contrary out before him and he would have defecated all over it. He would claim it was a stitch up designed to satisfy public opinion. People like that are not interested in changing their minds.
Fuck him.