Musar zu Dewarim 17:12

And now, should you not know for what [reason] one who transgresses against the words of the Sages is liable for the death penalty, more than one who transgresses [most of the Torah’s] positive and negative commandments? And this is the understanding of the thing: [It is] because one who transgresses against the words of the Sages has had the temerity to do so since their commandments are light in his eyes; and not from his impulse overpowering him. Rather [it is] since his eyes have been dimmed from seeing the light of their words, so he does not follow the light of faith and does not pull the yoke of its decree [upon himself]. So he does not toil to keep their statement, since it was not written in the Torah scroll. And he did not act like the one who transgresses the words of the Torah, about which his soul is bitter and taken away in front of him, such that he is afraid and frightened that his impulse moved him to sin. Therefore there is a sentence of death for a person who knocked down something from all of (His good words) [their good words]. And it is like he is saying, “Let us remove their ropes.” And it is similar to that which is written concerning the matter of the elder who rebels against the words of the Sages (Deuteronomy 17:12), “Should a man act presumptuously and disregard the priest, etc.”