This is an example of why this stuff is such a mess. He was about 18/19 when he posted that. We need to be forgiving of stupid shit people did and said when they were teenagers. Because of social media they stay around for ever when in the past people could move on from being idiot adolescents. Similar with Ollie Robinson and the crap he said.
As a general point not particularly about this case, I don't think it's helpful to be dragging people over coals for stuff they may have said years ago, particularly if they were young at the time. With Vaughan, as this was spoken and not written and not recorded in any way, it was always likely to end like this. Shahzad wasn't called as a witness, I don't think. He says he didn't hear any of the alleged words. He's also a great big tory prick, so I'm not sure I would trust Shahzad. But the point is that you can't trust any of their memories really.
Sometimes justice delayed is justice denied. I think this is one of those occasions. We can and need to learn from historic cases of racism and racist abuse, but we shouldn't necessarily be taking those cases into a courtroom.