Your own reasoning shows that morality is subjective, relative and depends on the situation in which one finds oneself. This is true regardless of the ad hominem arguments you have put forth. An ad hominem argument means that you attack the integrity of the person giving the opposite view, rather than addressing his arguments. It is used when you have no real answer to the arguments being raised.
I think you have shown here that the morality of NFP does in fact depend on the situation and the circumstances in which it is used.
But it is true in many more cases. Let’s take another example: The act of killing.
Whether it is moral or immoral will again depend on the situation:
I. A prison guard pulls the lever to the gas chamber of a duly convicted murderer. In this case his action is moral and there is no sin.
2. A soldier in battle defending himself in war shoots an enemy soldier. His action is moral and there is no sin.
3. A wife poisons her husband in order to collect the insurance policy and live with her new boyfriend. In this case the action is immoral.
So whether killing is moral or immoral is relative to the situation at hand.
No, it is not.
THere is an absolute in moral law and that is that intentionally killing an innocent person is morally wrong. A a person has a right to defend thenmselves from unjust aggression, up to and including killing the aggressor, but a part of moral law also dictates that lesser force is always to be applied if possible.
That in part has been the issue with number one, as John Paul 2 pointed out in his commentary on capital punishment - if the criminal can be successfully incarcerated (up to and including life imprisonment with no parole), that is to be used before the step of execution, and JP2’s commentary would make the execution immoral.
As to #2, there have been extensive questions about both the Viet Nam war and the last go-round with Iraq as to whether or not the war itself was morally justified, so your example is simplistic in a great amount; however, it is correct that killing the attacking soldier (all other things being equal) would be morally permissible; not because of the circumstances, but because the attacker would be an unjust aggressor. It is not the circumstances that make the moral law chageable; the moral law is the same - intentionally killing someone is limited by whether or not they are innocent or not.
Issue 3 resounds in the same.
What you are calling relativity is not about the moral law itself, but the issue of sinfulness or lack thereof.
The point of Relativism is that it denies that there is objective absolute truth. The Church holds to the contrary; if you doubt that, look at any number of repeated statements the magisterium has made about abortion. Relativism in denying any objective truth to morals reduces all conduct to a subjective valuation.
The Church holds that there is both objective and subjective issues of morality. The objective issues are revealed truth - the 10 Commandments are a prime example. The subjective issues are the individual’s action, and to repeat what the Baltimore Catechism taught, there are three elements of a serious, or mortal sin: 1) the issue must be serious (your example of killing suffices); 2) the individual must know that it is serious, and the individual must intend the act. That does not equate with Relativism, as relativism would deny that there arre acts which are intrinsically wrong. The church does not so hold. You can say that the Church then holds that morality is relative, but that is not within the definition of what Relativism holds.
A Relativist may define an act as morally good, or not morally bad, based on nothing more than a subjective relational determination between the two parties. The Church may say that the individual is not morally guilty of the act, but would say so for a far different reason. The Relativist is constantly trying to define the rightness or wrongness of an act by the changing situation; the Church says that the rightness or wrongness of an act is intrinscially determined as opposed to situationally determined. Abortion is always intrinsically seroiusly wrong and evil. The Relativist is never sure of the morality of an act as they ahve no absolute standard with which to compare; they deny there are any absolutes. Further, they have no way of responding why, if acts are supposedly moral in a given situation, that evil comes out of them.
And as to your comment about NFP, I satnd by my statement about logic. The morality of NFP is not right or wrong. The morality of refusing to be open to life is what is wrong, whether it is NFP, abstinenece in marriage, or a form of contraception. The Church holds that Contraception if intrinsically evil. The Church holds that NFP is not intrinsically evil. NFP does not become evil; the evil is in the intention of the party using it. Go back to my example about eating; eating is a morally good act; overeating is an issue of intent. Basic Church Morality 101 requires the ability to distinguish between the objective and the subjective. Relativism 101 denies that there is any objective; or if there is, that it simply does not matter (which is the equivalent of denying that it exists), and that only the subjective applies. Miss that point, ignore it or deny it and there is no intelligent conversation to be had.