and about the credibility of the Pentax US President? as far as i can tell the argument about this is weak. Saying that an author lacks the authority to write/say about a topic is a variant of ad hominem. The question is whether the author is correct or not.
actually to be fair, i don't think the ad hominem argument here isn't too horrible.
what is being seen here is called "ad hominem circumstantial":
http://www.nizkor.org/features/fallacies/circumstantial-ad-hominem.html
i think there's nothing wrong with questioning a source when there is credible reason to believe that the source may be necessarily biased because of the position of the source.
i quote:
There are times when it is prudent to suspicious of a person's claims, such as when it is evident that the claims are being biased by the person's interests. For example, if a tobacco company representative claims that tobacco does not cause cancer, it would be prudent to not simply accept the claim. This is because the person has a motivation to make the claim, whether it is true or not. However, the mere fact that the person has a motivation to make the claim does not make it false.
what i wish to highlight is the last statement - just because someone from pentax made the claim, doesn't mean that the claim is necessarily false - to assume so is the error, not asking for prudency in addressing the claim.