I think there are two aspects emerging from the discussion:
1. Does the individual suffer from dementia to the point where he cannot stand trial ?
As I understand it 4 consultants have examined him and found that he is unfit to stand trial (or whatever the expression is), two appointed by the family and two appointed by the CPS. Personally I would find it difficult to argue that they are wrong (given that they are experts and have examined the individual and I suspect most people claiming he's faking it are not experts and have not examined him. I can only rely on the diagnosis of these experts, but I can say that I have personally been shocked at how fast dementia can progress; it seems that (some) sufferers cope with a fair amount but suddenly a slight progression means routine tasks become just too much and everything seems to fall apart.
2. Should he stand trial and if found guilty be punished anyway.
That would seem to be a matter of law. From what I've read, were a trial to happen and were he found guilty the courts would realistically have only one sentencing option "absolute discharge". An interesting excerpt from a legal blog on the issue
http://barristerblogger.com/2015/04/16/lord-janner-was-the-dpp-right-what-can-the-complainants-do-next/ wrote:Any prosecution would be an expensive and time consuming process and it could not prove Janner’s guilt, or require the Court to punish him. The inevitable result would be either his acquittal or (far more likely given his inability to contest the evidence) a finding that he had committed the acts alleged, followed by his absolute discharge. What is more – although Ms Saunders did not say this – the trial of a man unable to defend himself while a succession of witnesses made a series of unchallengeable allegations against him would be a fairly grotesque parody of justice.
(I found the full article interesting because it did not seem to be arguing that Janner should or should not be prosecuted, but rather it discusses the legal considerations.)
Personally, as to how this should progress in the world according to me ... I really don't know. I can see strong arguments for both sides.
Ian