A few years ago now one of my old bosses was a retired Captain out of the army, and even though he was "now" in civvy street he still used that title in his letterheads.
I told my elder brother {a retired army warrant officer} about it and he said "Why shouldn't he, he's obviously earned it, and you'd be surprised at the doors a title can open for you".
So I'm not surprised people accept titles Clegg is just one of many who thought if you cant beat 'em join 'em.