Unfortunately, you have to pay to get online access to these letters. Messina generally appears to be a soy advocate, so he may have been questioning the study conclusions (soy protein reduced testosterone). I saw the original study myself, but there were others published around the same time coming to opposite conclusions. The contradictory studies on soy continue to be a source of frustration.
These studies raise a potential issue that has prompted me to keep my soy protein intakes at a lower level. Still, I have had good results using it in the past, so you have to wonder.