I used to think I was a very firm deontologist, but that was mainly because I didn't want ethical rules to be bent willy-nilly to maximize something simple like "number of lives saved." I didn't, for example, want torture to be legal. I wanted to live in a world with "rights" -- that is, ethical rules that ought not to be broken even when the circumstances change, for all possible circumstances with non-negligible probability. You don't want to live in a world where people are constantly reconsidering "Hm, is it worth it at this moment to not steal Sarah's property?" You want to live in a world where people understand that stealing is wrong and that's that. You want some rigidity.

I think a lot of self-identified deontologists think along these lines. They associate utilitarianism with "the greatest good for the greatest number," and then imagine things like "it is for the good of this great Nation that you be drafted to dig ditches this year" and they shudder.

That shudder isn't necessarily a "confabulation." The reason you shudder at the thought of a moral rule to "maximize utility" is that there is no definition of utility or "human value," simple enough to state in one sentence, that wouldn't result in a hell-world if you systematically maximized it. Human value is complicated, as this site has been at pains to tell us. Pick something (like "number of lives saved") and optimize for that, and you won't like the results.

People come up with deontological constraints, I think, to deal with the fact that "maximizing utility," when you visualize it, looks very, very bad. Modeling utilitarianism to low precision looks bad. Adding more subtlety to the model might not be so bad. Adding in terms like sympathy, respect for life, and so on as positive goods, so that throwing someone off a trolley is not a clear win. Or you could model human value by appealing to rights. Either way you haven't really put your finger on what you mean by "moral." If we could define morality rigorously, life would be easy, and it isn't.