Re: A person of reason, he is.
Read his CV please. He, and his friends, wrote most of the instruction manual being used by the UK security services. Or, more accurately, collated what they were/are doing into one place and brought it into the open.
Now if he is such a smart person (and he does seem to be) then you have to ask whether he's doing this because he's seen stuff that makes it clear these measures are justified, or that he's pushing as far as the political realities allow.