Thatcher may have been wrong over certain factors to do with the Falklands. She should have been honest about the Belgrano. It was a threat: we sunk it. End of. Sad but very true. As for the loss of life. Well that is to be regretted on all sides and can never be justified. But we have been in far worse places morally since.
With respect, you seriously need to review this. The Belgrano was not a threat when Thatcher ordered its sinking (an event which she encouraged us to rejoice over - remember?) And you sound just like the most cynical of cynical politicians when you "regret" the "loss of life" (aka "needless slaughter??"). Every one of those hundreds of young men had a mother, you know. Your final sentence of the above quote would be a challenge to enlarge upon too.