he was basically making his patients hyperthyroid

Why is this a reason not to reject it? He is essentially arguing that the major cause of cardiovascular disease is population-wide high rates of hypothyroidism. It would be a circular argument to dismiss that because his treatment leads to a greater than average metabolic rate. One would also need evidence of a disadvantage that outweighs the advantages. His patients seemed to be doing well, or at least he doesn't report them exhibiting any classic signs of hyperthyroidism. He was primarily adjusting dose based on body temperature to the upper end of the normal non-hyperthyroid range.

to help them lose weight

I have seen studies on thyroid supplementation as a weight loss strategy, and it causes loss of lean tissue (muscle, etc.) more than fat.