What’s tripping you up here is thinking that venial sins are violations of God’s law. So you’re not yet seeing the basis for the difference between mortal and venial sins. Venial sins are not violations of the law; they are not violations of love. They are deficiencies or defects in carrying out the love that is the spirit and principle of the law. So to view venial sins as merely more rule violations is to approach the whole question through the list-paradigm, rather than through the agape paradigm, which gets ‘behind’ the list to the spirit or principle (i.e. agape) of the law, thus allowing for a distinction between actions that violate this spirit, and those that are still ordered by this principle but fall short of its perfect expression.
Bryan explains further.
Venial sin in relation to God is very much like doing something minor or unintentional that troubles one’s spouse but does not break the friendship with one’s spouse (say, failing to remember to readjust the seat in the car, so that it is easier for the other person to get in). It is not a violation of the law of love. When you get into the car and find the seat not readjusted, you don’t justifiably turn to your spouse and say, “You violated the commandment to love your neighbor as yourself.” That would obviously be way over the top, because the failure was not purposely chosen out of spite or apathy; the spouse loved and loves you, and the inaction did not destroy that love or indicate its absence. But neither is failing to readjust the seat, if one’s spouse has requested that one do so, a perfect conformity to love for one’s spouse. And in our friendship with God there is a similar kind of distinction between two types of sins: mortal and venial.
This is fudging. It's also merely a "venial sin" to tell your little sister that you hate her; this is not merely not re-adjusting the car seat. And yet it will net you simply a couple of Hail Mary's in the confessional.
And yet it is thoroughly a sin according to Matt 5:21-22. This is a clear example of Bryan's "Tradition" negating the Word of God.