Montolivo moved from Fiorentina this summer.
"After seven years in Florence, the club put me in a bad light with the fans," he told Sportweek.
"They put the blame on me for the fact I would not renew the contract, but it simply wasn't fair. It could've gone differently, but they didn't want to meet me half-way.
"The thing that hurt the most in my Viola experience was when they took the captain's armband off me.
"However, the worst moment was when the threats started appearing on the walls outside the training ground and on the Internet forums.
"Playing in Florence is not easy. At least after this experience I need never fear anything in sport again."