I am addressing it by suggesting that there is no such moral teaching of the Church. Is any sin justified by sufficiently grave reasons? That is not Church teaching. It may be your own, but not the Church’s.
I have referenced official Church teaching that says lying is wrong. You have disagreed, but have not provided any references to support your assertions, only your own beliefs, which I am pointing out are not in alignment with the moral teachings of the Church.
With regard to the “this is/isn’t church teaching” issue, this is not sound reasoning, since no reasoning of any sort goes into a mere reiteration of dogmas, but even within those extremely limited boundaries, it is possible to make mistakes, and your mistake is in taking the catechism -absolutely literally.-
You see, the funny thing about 2464 of the catechism, and several other points in it, is that if taken to its literal extent, it leads to absurdities. For example, it says…
“The eighth commandment forbids misrepresenting the truth in our relations with others.”
Now, if you interpret “misrepresenting the truth” to mean “saying something false” (the literal interpretation,) then you may have committed a mortal sin tonight while reading your children a nursery rhyme.
For example, if I tell my son “Jack and Jill went up a hill to fetch a pail of water.” Well, wait a minute! If Jack and Jill -didn’t- go up a hill, or if one went up, but not the other, or if they went up the hill for some reason other than to fetch a pail of water, then that’s a falsehood! In fact, since the nursery rhyme is utter fiction, it’s almost -guaranteed- to be a falsehood.
Now, am I to affirm that telling nursery rhymes to my children is a mortal sin? Is that grave matter? Well, I think the answer is “obviously not.”
Now, why is this not grave matter? Simple. It’s because of your -intention.- Your intention is not for anyone to be hurt, slandered or led astray by the nursery rhyme. The same applies to other kinds of falsehoods.
A thorough study of the church’s teaching on the hierarchy of human rights clarifies this further, as I previously explained.