I wouldn't think that, everyone is entitled to their opinion. My personal view on him is not dissimilar to yours but I just could not imagine a situation where I wouldn't support a Blades player, and certainly not cheering a goal by them. I even cheered when Marlon King scored ffs.
I also think character and due diligence plays a huge part in Wilder's signings and I sincerely doubt he would have taken a nobhead on board. He also isn't blind to what happened before but people can change. I had old mates who behaved like utter cocks when drunk, always starting trouble and treating girls like shit. I wouldn't want to be anywhere near them if they were still like that but they grew up and sorted themselves out. That doesn't make what they did ok, or fix the damage they caused to people along the way but life goes on.