I kinda get what they feel. When someone falls in love for a football club, it's because of it's philosophy. The spirit of the team and it's players. The club's identity both on and off the pitch. Once that is gone/replaced with something different (better/worse), it's natural people start questioning/feeling differently about the club. Think about the Manchester United/FC United story.
I won't be surprised to hear people saying they've lost their interest in Juventus.
I know I won't lose mine, but I also won't condemn people who can't relate to the club's way of doing things anymore for doing it.
That being said, it's still too soon yet to know/judge what Juventus is becoming.