traditionally Juve and Milan are the biggest serie A teams and despite historically competing there was generally never bad blood and enmity among the clubs and fans. Also because Juve traditionally dominates more domestically while Milan focused on CL.
This changed after the 2006 scandal when Juve was relegated and Inter and at a lower degree Milan took advantage of the situation, despite being more heavily involved in the same type of behaviours for which juve was destroyed. That soured the relationship because Milan went on winning their 7th CL despite being found guilty in the same year of our relegation. Of course at the time the head of the government happened to be Milan president and the head of Italian FA a former member of Inter board of directors.
Since then relationships have gone south worsened by an episode in 2012 (first Conte's title) when a regular goal was disallowed to Milan against us.
So while we do not have the same type of deep rooted hatred we have for the joke of Serie A that is Inter, there is no more love left with Milan either
Bonucci transfer to Milan is a massive blow that goes well beyond the technical aspect because Bonucci has been one of the leaders of this Juve's cycle and he has been the most vocal supporter of juve's values often going to see matches among the fans when he could not play. He was supposed to become captain next year after Buffon will leave, but clearly there was a fall off with the coach and the club and along with the silly money offered by Milan he decided to go. You do not wanna read his and his wife's social feed these days for the amount of abuse they are taking by fans
Not really classy I know but it is a sign of how much it hurts. Of course we would have preferred he went to Chelsea or City, but they did not want to move from Italy and Juve clearly wanted to get rid of the problem asap. I think the club should have pushed more for a transfer abroad, it is a big mistake