Cologne granted the 23-year-old’s request to cancel his contract on Friday after he was confronted outside his flat by a group of angry fans.
“A group of people ambushed him outside his private residence this week, roughed him up and really threatened him,” said Cologne coach Stanislawski.
“That is just not acceptable and can’t ever be so.
“They left a note on his car and made it clear they wanted to really hurt him.
“These people have crossed the line.”
Having joined Cologne in 2008 from Blackburn Rovers, Pezzoni, who had his nose broken by a fan in February while celebrating in the city, told Stanislawski he no longer felt safe playing for the the club.
“He told me that every ball he played meant more to him than just not making a bad pass. That is not acceptable (for a player),” added the coach.
Pezzoni has not commented on the incident, but wrote on his Facebook page on Saturday: “I am delighted to read how much understanding there is for our decision and how much incomprehension there is for bullying and verbal abuse.”
Having been relegated last season from the Bundesliga, Cologne lost 1-0 at home to Energie Cottbus on Friday, their third defeat in four games.