I find it impossible to judge from the article in the Mail.
I've watched some of the video footage and thought that the man's manner seemed belligerent and confrontational right from the start.
He may well have an exemption, medical or otherwise, but he did himself no favours at all. I would have thought that the place to start would have been by calmly explaining that he was exempt and taking it from there. Instead, he seemed aggressive and defensive pretty much immediately.
I am not saying that the police behaved impeccably, nobody did. I would wonder if there might be further background to this that is not evident from the media reports and video clips? Perhaps he is already known to police for other things?