The argument for not pardoning is mostly reasonable, I think. It was a crime at the time, and you can't go around posthumously pardoning everyone retroactively whenever the law catches up to society a generation or two later. (Edit: I still think what they did to Turing was wrong, of course.)
Not a brit, so my opinion is officially meaningless. But, why can't you just go around issuing posthumous pardons for unjust old laws? I mean, it's posthumous! It's not like there's a fundamental fairness issue at stake here. Other unjustly-convicted dead people aren't suddenly going to file suits demanding redress.
Just do the right thing. Why bother with the technicalities?
Two things because the person is already dead pardoning them isn't going to do a lot of good for them is it? Furthermore the governments opinion that convicting them was wrong is already apparent due to the fact that they changed the law. Next, England is one the oldest governments on Earth being roughly 1000 years old (give or take a century), individually pardoning every dead person who committed a crime that is no longer a crime would be a major burden on the parliament taking time away from addressing the needs of living people. As a result it makes a lot of sense to have a blanket (and longstanding) rule; no pardons for dead people.
Your opinion is not meaningless although like 99.9999% may be ultimately ignored.
But the problem with pardoning people posthumously for something is that there may be people who were convicted of the same crime who aren't yet dead. A government admitting that it did wrong is just asking to be sued. Sorry quite cynical I know.
http://www.forbes.com/sites/carolpinchefsky/2012/02/07/uk-de...
The argument for not pardoning is mostly reasonable, I think. It was a crime at the time, and you can't go around posthumously pardoning everyone retroactively whenever the law catches up to society a generation or two later. (Edit: I still think what they did to Turing was wrong, of course.)