The deontologist and consequentialist approaches to morality need not exclude each other, and I don’t think they do.
They do exclude each other. The deontologist says that morals cannot be justified by consequences. The consequentialist disagrees.
Wikipedia offers the following description of deontological ethics:
Deontological ethics or deontology is the normative ethical position that judges the morality of an action based on the action’s adherence to a rule or rules. It is sometimes described as “duty” or “obligation” or “rule”-based ethics, because rules “bind you to your duty.” **Deontological ethics is commonly contrasted to consequentialism **and virtue ethics. Deontological ethics is also contrasted to pragmatic ethics. In this terminology action is more important than the consequences.
"Charlemagne III:
The only consequentialist position that is too extreme is the notion that “the end justifies the means.”
A simple counterexample is spanking one’s child. The end, having a disciplined child, presumably justifies the means, inflicting pain. The discipline of a child is particularly special in that you can’t argue that you’re “doing justice” to the child. Children don’t know any better, so you can’t even argue that they deserve the spanking. Rather, they are spanked so that they will know better in the future.
As for your example of Hitler trying to justify his means, that is a case of the means outweighing the end. There is no morality that says you can ignore the means altogether, at least none that I know of. You have to compare the evil of the means with the good of the end.
So there are consequential moral acts that are not justified, and that happens mainly when “the end justifies the means” comes perilously close to the utilitarian argument of the greater good of the greater number of Germans over the lesser good of the lesser number of Jews.
This is a flagrant strawman of utilitarianism. As I’ve said numerous times, utilitarianism doesn’t care about one’s nationality, race, etc. It attempts to maximize the happiness of all sentient beings, not just Germans, or Americans, or Jews, or Caucasians, or even humans.
As a matter of fact, “no man is an island entire unto itself.” We have to trust the judgment of others because we cannot each of us re-invent the moral wheel. The question is whom we are to trust. I’ll go with the Catholic Church over the Society of Moral Relativism.
My point is that you cannot deflect your own responsibility to choose a moral code onto another entity. You can follow the Church’s teachings. When a bishop speaks, you can agree with what they say. But following and agreeing are your choices. You are still ultimately using your own judgment, so you are still the arbiter of your own morality. You are no better off than the atheist who chooses his own morality.
Using myself as an example, I’m puzzled that you think we atheists isolate ourselves. What do you think I’m doing right now? I’m debating morality with someone whose opinions are vastly different than mine. I’m exposing myself to different perspectives, figuring out what works and what doesn’t. How is that isolation?