Parshat Acharei Mot

Parshat Acharei Mot
Vayikra 16:1-2 (Robert Alter, trans.)
And the LORD spoke to Moses after the death of Aaron’s two sons, when they came forward before the LORD, and died. And the LORD said to Moses: “Speak to Aaron, your brother, that he may not come at all times into the sacred zone within the curtain, in front of the Cover that is on the Ark, lest he die. For in the cloud I shall appear over the cover.
Robert Alter
As Rashi, Abraham ibn Ezra, and many traditional and modern commentators variously observe, the death of Aaron’s sons when they presumptously entered sacred space is mentioned to alert Aaron to the mortal danger he and his successors run in entering the Holy of Holies on the Day of Atonement.
After the death of Aaron’s sons: Why did the Torah say this? R’ Elazar ben Azaryah would explain it with a parable. It can be compared to a sick person to whom a doctor entered to treat. The doctor said to him, “Do not eat cold food, and do not lie in a damp chilly place.” Another doctor came and said to him, “Do not eat cold food, and do not lie in a damp chilly place, so that you will not die the way that So-and-so-died.” This second doctor roused him to follow his instructions more than the first. This is why it says, “after the death of Aaron’s sons.” 
Most of the midrashic discussion follows what is described by Alter and Rashi; the sons committed a sin and Aaron is being warned to be scrupulous is in his behavior at the Holy of Holies on Yom Kippur. However, there is a midrash that takes a different view:
Midrash Tachuma, Acharei Mot 5:1
“After the death of Aaron’s two sons.” R. Berehyah opened his discourse with Proverbs 17:26: “To punish also the righteous is not good; to smite the noble ones for uprightness.” Said the Holy One, blessed be He, “Although I punished Aaron (for the golden calf) by taking his two children from him, it is not good. It was only  “to smite the noble ones for uprightness.”
Midrash Vayikra Rabbah 20:10-11
Now did they really die before Hashem? Rather, before Hashem teaches that it is difficult before the Holy One, blessed is He, when sons of the righteous leave the world in the lifetime of their father. … they received their death sentence at Mount Sinai. And why did they not die at that time? This can be explained by a parable. It may be compared to a king who was marrying off his daughter, and it emerged that her best man had been involved in disgraceful behavior. So the king said, “If I kill him now I will mar the happiness of may daughter.”  Rather: My time of happiness will be arriving tomorrow, and it is better that my happiness be marred and not the happiness of my daughter.” 
The sin is Aaron’s at the Golden Calf incident.  What tension might the midrash be alluding to?