Breathing in through your nose has many medical benefits over mouth breathing. As usual, be wary of misinformation and bias when looking up health on the internet.
People with the same condition can respond differently to the same treatment. This is why personalised treatment is so important in all fields of medicine, including psychology.
In an era when opinion often trumps evidence in public health issues, it's time to support and invest in evidence-based medicine to protect the public from dangerous, poorly informed beliefs.