According to Osho, he doesn’t oppose Gandhi the person; he challenges our attachment to him. When we idolize any master, slavery to names replaces freedom. He speaks sternly about Gandhi, Ram, Buddha, and others to break clinging, so seekers stand on their own feet—nobody, label-free—and become available to God directly rather than to sects and followers.
I speak against Gandhi so you stop worshipping people and find your own inner strength and direct connection to God.