Ah, what a beautiful example of a straw man. The title of this thread is “How far must one listen to Gedolim”, while I’ve never even heard of most of the Rabbonim on that letter.
So
1. ZD seems to think that every Rabbi is a Gadol. Pretty fanatical viewpoint.
2. Being that being a Rabbi in no way means that the Rabbi is a Gadol, the whole question is irrelevant. No one ever said you have to do everything said by any Rabbi.