In regards to estrogen, the compounds ‘daidzen’ and ‘genistein’ are the culprits, researching these may bring more to light. Many people avoid them like the plague, and the benefits unique to soy are minimal to none, so I figure that better nutrition can be found elsewhere.
In regards to the thyroid, I believe that said two compound are also implicated in toxicity of the thyroid, soy is known to be a goitrogen, a compound with an affect on goiter formation.
Finally, for acne, I have not heard of soy directly causing acne. However I am not too versed on skin health (my face can validate that for me), it may be a downstream effect of estrogen though, as my face has cleared up with Zinc supplementation, Rez-V supplementation (at 3 pills/day), and now TRIBEX. All of which affect my Test/Estrogen profile for the better (The first being a mere deficiency avoidance)
As for ‘detrimental to health’; If you put it into a cost/benefit analysis, one would be hard-pressed to find them optimal in any situation, as better nutrition can pretty much always be found elsewhere. They won’t make your progress stop or health significantly deteriorate, but they are never the best option.
(Finally, I have heard the above does not apply to fermented soy products, but do not know why)