But I don't think Mr Cameron need worry too much about a minority expressing themselves in this way. Overall, public opinion is not sympathetic to criminals, particularly the likes of Moat. It will be difficult to find any news headlines bemoaning his death, even though he has evaded the justice of the courts.
What he might consider, though, is the reaction of Moat's uncle. Understandably upset, he has said "what he has done is terrible, but he didn't deserve death". This also is unlikely to win many people over. Even those who tend to agree might want to add that he didn't deserve death, but neither did the man he killed, and the others he attempted to or intended to kill. But there is still some truth in what he says.
The words of Moat's Uncle remind me of a quote from The Lord of the Rings. The book is not everyone's cup of tea, but bear with me, for the words stand up well in any context:
"He deserves death."
"Deserves it! I daresay he does. Many that live deserve death. And some that die deserve life. Can you give it to them? Then do not be too eager to deal out death in judgement."
There is real wisdom in this, reflecting the teaching of Jesus and the New Testament. Who are we to give or take life? We are not God. Moat, of course, was guilty of this. He took life that was not his to take including, at the end, his own, the final act of a man without hope. We could condemn him for this, or we could simply recognise the truth of these words instead, and refrain from judgement. We might even spare a little compassion for Moat (although not at the expense of compassion for his victims), barely imagining what it must be like to be in such despair.
I'm also reminded of Jesus saying "let him who is without sin cast the first stone". Of course Moat's actions were evil. But we have a system of law and justice to provide a good framework for condemning this kind of behaviour. As soon as we take it upon ourselves to pronounce judgement on someone else, then we are uncomfortably close to sounding sanctimonious.
I can completely understand why Cameron is revolted by the hero-worship of Moat. But as much as we shouldn't canonise him, we shouldn't demonise him either. He was one of us, something which is cause for humility, not celebration or condemnation.