Sorry, I forgot to reply to your post. I have so many people berating me here that it is quite easy to do that. 
Bishop Williamson was not appointed by the Pope. He was illicitly ordained by Abp Lefebvre and is a bishop forever. The Pope has no jurisdiction over him so he ignored being suspended 'a divinis' by Pope Benedict. His immediate superior, Bishop Fellay has expelled him from the SSPX and as he has ordained two more bishops recently he has once more incurred excommunication. Were he a layman now I would not expect him to be accepted even for the priesthood.
I do not like judging a person's worthiness on account of the state of my own soul. I studied for the priesthood and had I become one I'm sure most people here would find me lacking in worthiness.
The point I was originally making was that +Williamson was not initially or subsequently excommunicated for denying the Holocaust. It was on account of his breach of Canon Law in receiving episcopal ordination illicitly.