The BVB chief criticized the timing of the Germany international's decision to swap Bundesliga clubs and insisted Marco Reus is going nowhere.
The prodigiously talented 21-year-old agreed to swap Signal Iduna Park for the Allianz Arena for an estimated 37 million euros in April, just before a crucial Champions League semifinal game with Real Madrid.
The move angered many BVB fans and Zorc admits it was frustrating to know Gotze would leave but criticized the extreme reaction in some quarters.
He told Bild: "Of course we were disappointed about his decision to leave us - especially about the timing. One has to admit that. However, the vilification of him I condemn in the strongest terms. I have recently congratulated him for his birthday [June 3]."
Zorc shot down suggestions that Gotze's fellow Germany international Marco Reus might be the next star exiting Jurgen Klopp's squad.
"We have long-term plans with Marco, which is also discussed with him that way," he insisted.