sp - This may be interesting to look at:
http://news.bbc.co.uk...d_8811000/8811495.stm
Of the notes you can read, several of them appear to be from people who knew him personally or had met him in some capacity. I guess it's long been known that even monstrous serial killers (e.g. Bundy, Shipman) always appeared well-balanced and pleasant people. I'm no expert, but I'm willing to bet there's a degree to which people are mourning the fact that they feel they've lost that side of Moat's personality.
While I think it's pretty rare, to take another example you sometimes hear of similar psychology in abusive relationships - the victim sometimes continues to love aspects of the abusive partner's personality, while almost learning to ignore the horrific side. That's quite a different scenario to this one, but I'm willing to bet there's something a little bit like that there.
(Disclaimer: Before any of them jump on me, I am well aware that there are ABers who have left abusive relationships. I am not asserting that this always happens or that it's even common [I have no idea how frequent it is]. But sometimes you do hear of it. I also neither condemn nor condone any of what I've described )