For better or verse?

The mishnah at Avot 5:21 contrasts those who cause the community to act in an upright and responsible manner with those who lead them down the path of sin and error. Translated, it reads like this:

One who causes the community to be meritorious, no sin will come through his hand, while a person who causes the community to sin is not given the opportunity to repent.

Having stated the basic principles, the mishnah then brings verses in support of them: 

Moses was meritorious and caused the community to be meritorious, so the community's merit is attributed to him, as it says "He did God's righteousness, and His laws with Israel" (Deuteronomy 33:21). Jeroboam the son of Nebat sinned and caused the community to sin, so the community's sin is attributed to him, as it says, "Regarding the sins of Jeroboam, which he sinned and caused Israel to sin" (1 Kings 15:30). 

The two support verses appear to be cited in order to suggest that Moses caused others to do good while Jeroboam (illustrated, right, by Fragonard) did quite the reverse. Do they actually provide this support? Neither verse actually refers to the consequences of Moses' positive leadership and Jeroboam's adverse reign. Moreover, the first verse does not even refer to Moses. From its context in Deuteronomy it is clear that it refers to the tribe of Gad. Any connection between this verse and Moses himself is purely midrashic, since it seems to date from Midrash Tanchuma, Shemot 28. 

The fact that this verse does not, scripturally speaking, apply to Moses does not appear to trouble the major commentators. Rambam, the commentary ascribed to Rashi, Rabbi Ovadyah Bartenura, Tosafot Yom Tov and Rabbi Shmuel di Uceda are among the many luminaries who pass no comment on this at all.