The 38-year-old responded to the Bavarian club's negative comments by claiming they are still reeling from the forward's decision to join rivals Borussia Dortmund next seasonBorussia Monchengladbach sporting director Max Eberl believes Bayern Munich are bitter following Marco Reus' decision to join Borussia Dortmund in the summer.
The Bavarians were keen to land the 22-year-old, but the attacker decided to commit his future to the German champions instead.
Bayern CEO Karl-Heinz Rummenigge and defender Holger Badstuber have publicly expressed their disdain at Reus' decision, but Eberl condemned their comments, claiming the club are still trying to bounce back from the disappointment.
"Among the many clubs that were interested in Marco, Bayern were the most publicly committed," said Eberl.
"That they taunt him now shows that they have found it difficult to cope with his decision."
Gladbach will resume their Bundesliga campaign against Bayern at Borussia Park on Friday.