Who needs the Golden Rule? Certainly not everyone. The Buddha or the enlightened one doesn't need one. Golden Rule is only for those in need of a sticky reminder specially at times of almost intolerable situation, wherein one needs to remind own self to try really hard not to cause ruin to others, both in action and intention, except in self-defense. Willful act of injuring other men or retaliation is a big no if Golden Rule is to be followed devotedly.
The Buddha no longer needs Golden Rule for himself obviously. There is a simple reason for that. He already realized the spontaneity of everything including Golden Rule. Having fully understood the truth of his Being, the Buddha is already free from the struggle of making an effort to abide by the Golden Rule. Interestingly, the Buddha is already the embodiment of the Golden Rule. For him, everything flows not by effort or willful exertion or vigilant self-restraint but everything including love, compassion and respect goes on and on so naturally like a breath.