Despite what we teach small children, lying is not immoral. Lying is amoral. The circumstance and motivation of a lie determine whether that particular lie is moral or immoral.
There are times when it's moral to lie, other times when it's immoral to lie, and still other times when morality hardly has anything to do with it at all (such as the above scenario.) We tell small children that it's immoral to lie because we don't trust their moral judgement and would prefer they always tell us the truth.
I don't think people grow out of the need to follow moral rules as much as you imply. Sooner or later, there comes a time when it is overwhelmingly in a person's interest to lie (or some other transgression). If they are purely rational, they will do it. If they think deeply about morality, they will rationalize why it is right to do what is in their interest. The point of inculcating honesty and other virtues is so one is habituated to the point that dishonesty is preempted when it really counts. Reasoned moral judgement is not an unmitigated good, because it opens the way for bias and hinders the operation of trust needed for relationships.
The way I see it, telling a "harmless" or "justified" lie can destroy trust, which can have substantial or even devastating consequences. Often one faces several choices, all of which may hurt people, and moral rules are a heuristic method by which people avoid the harmful effects of cognitive biases due to self-interest or logical errors.
None of this should suggest I think it's obviously wrong to lie to a stranger about whether you're deaf in order to avoid a conversation - that might be permissible according to generally accepted social rules. My point is more that when you start talking about deciding for yourself when to obey moral rules, you are on shaky ground, no matter how wise or logical you are.
> Lying isn't bad. Hurting people is bad. There are many totally honest ways of hurting someone.
While I agree with your first two sentences and think that they are well said, the third doesn't demonstrate the first; it demonstrates only that "hurting people can be done without lying", not "lying can be done without hurting people."
Is it ever morally acceptable to tell a lie? Kant thought not. His example of the would-be murderer explains his reasoning. Read by Harry Shearer. Scripted by Nigel Warburton.
Thankfully most people have more sense than Kant. In truth, I doubt Kant himself would be so hardline if he were actually put to the test in such a scenario. Talk is cheap, would he actually be so depraved in practice? I can't rule it out, but I doubt it.
Kant's philosophy is universal, not individual. His morality (and many others!) accepts that people may becomes martyrs.
Should you kill a person to save two? Kill two to save one? Does matter who the people involved are? Anti-Kantian philosophies don't have good consistent answers to this -- at least they don't live according to their philosophical answers.
There are times when it's moral to lie, other times when it's immoral to lie, and still other times when morality hardly has anything to do with it at all (such as the above scenario.) We tell small children that it's immoral to lie because we don't trust their moral judgement and would prefer they always tell us the truth.