The law of non-contradiction is essential to rational thought. A thing cannot be simultaneously be and not be, or otherwise belong to mutually exclusive categories at the same time. However, it would seem that many people try to violate this law daily.
Moral relativists of all stripes are contradictionists (that's a word now). To claim that there are no absolutes is an absolute statement and a contradiction. Catholics who contracept may employ a variety of obfuscating concepts and terms such as "conscience" or "the spirit of Vatican II" but when it comes down to it, they are attempting to affirm Catholicism while simultaneously denying it, a violation of the law of non-contradiction.
In his Metaphysics Aristotle says that someone who would deny the law of non-contradiction cannot in speech "signify something both to himself and to another," without affirming the law they would refute. To maintain the fantasy of contradiction, he must "speak of nothing."
If he speaks of nothing, it is ridiculous for us to seek to engage in rational discourse with someone who doesn't engage in rational discourse with someone who does not engage in it' for insofar as he does not engage in any rational discourse, he is like a plant.By denying the law of non-contradiction, a rational animal negates any attempt at reasonable speech.
This doesn't mean that those who inadvertently violate the law of non-contradiction are all imbeciles, but that in particular areas they fail to use their rational faculties. The aforementioned Catholic dissenters may be quite rational in other respects, but when they try to address issues of moral theology they are about as useful as a zucchini.
Be a person, not a plant.