Because arbitrarily banning a sannyasi "in good standing" within ISKCON by ISKCON authorities, is offensive, unfair, in bad taste,and a clear case of "maryada vyatikrama", as described by Prabhuada in his Purport in Srimad Bhagavatam, 3.4.26: Srimad-Bhagavatam, Third Canto, Chapter Four, "Vidura Approaches Maitreya"
26 - Sri Uddhava said: You may take lessons from the great learned sage Maitreya, who is nearby and who is worshipable for reception of transcendental knowledge. He was directly instructed by the Personality of Godhead while He was about to quit this mortal world.
PURPORT - Although one may be well versed in the transcendental science, one should be careful about the offense of maryada-vyatikrama, or impertinently surpassing a greater personality. According to scriptural injunction one should be very careful of transgressing the law of maryada-vyatikrama because by so doing one loses his duration of life, his opulence, fame and piety and the blessings of all the world.