Is there a point at which a person can rightly dismiss a philosophical statement or even an entire philosophical system because it originated with a person of dubious character or intent, but (here's the catch) without committing the ad hominem fallacy in doing so? I am thinking of extreme examples, such as (alleged) philosophical systems created by, say, New Age healers, cult leaders, etc. Or, conversely, would it be necessary even in these extremely examples to address only the philosophical claims made by these movements -- one by one -- instead of addressing the character of the founders themselves in order to avoid the ad hominem?