he is a cardioligist, which has very little to do with immunology or virology. An analogy ( for this forum ) would be a Ruby on Rails developer providing a critique on memory management in embedded systems. He can have his opinion, but just because he can be called "doctor" does not mean he knows everything about human physiology and pharmacology. If he had a strong opinion about heart health and cardiovascular disease (such as the debate around saturated fats) then I would give his opinion a high level of confidence.