The gemara says that Ovadiah HaNavi prophesied against Edom because he came from there and therefore their destruction was done as an "inside job" [מיניה וביה אבא ליזיל בה נרגא - See Sanhedrin 39b with Rashi that it is compared to someone who cuts down the trees in the forest with an axe whose handle is made from a tree grown in the forest].
Esav sold his rights to the bechorah because he feared that if he drinks wine and serves Hashem by bringing the korbanos [as the bechoros used to do], he would die [as the the law for those who serve after drinking -שתויי יין]. So Esav sold the bechorah and received his wine. Now he could drink to his hearts delight.
On Purim we fulfill the mitzva of erasing Amalek [Esav's descendant] by taking his wine and drinking it.
An inside job. We use HIS wine to erase him.
Li-chaim!!!!
[Maran HaRav Hutner ztz"l at his Purim Seuda 1970]
לזכות אברהם מרדכי בן נעכא גיטל