I would agree that hot yoga is not for everyone and would generally agree with the points made by the writer.   And, actually, it can be dangerous for some people because the mechanism that promotes detoxification in most people when conditions are hot, instead, reverses and causes toxicity and health problems in people who have certain genetic anomalies.  

People with normal genetic expressions around heat shock protein do well in saunas for detox.   Those who have anomalies can make themselves ill in a sauna or in very hot weather and are more vulnerable to failure of their detoxification mechanisms.   This is why some people get heat stroke easily while others do well in the same weather.  If you know anyone whose body shuts down in hot weather, that is heat shock protein in action. 

So, the normally protective effects of heat shock proteins do the opposite in people whose genetics are expressing abnormally, for whatever reason.   This is an area that is not yet fully understood.