There are lots of lies in the Bible about Jesus and unfortunately many 'muslims' have not studied this properly so go along with the many false narratives in it.
61:14 O You who have chosen to be blessed with belief! Be God’s helpers. As an example - Jesus son of Mary said to the disciples, “Who are my helpers for God?” They said, “We are God’s helpers.” Thus a group from the Children of Israel accepted him, and another group rejected him. Then We strengthened those who believed, against their
foe, and they became triumphant.
Those who stand up with you, after careful thought, become dutiful to that person and his cause so could not, did not, would not deny him.
Backbiting, particularly his noble real disciples, is a sin in the Qur'an.