It isn't the argument's validity, but the source's trustworthiness. These are related but not the same; the source's trustworthiness is a contributing factor to whether or not I want to spend (waste?) the time verifying the validity.
Oh, nonsense. It's entirely about the argument's validity, and this bit about the source's trustworthiness is a red herring. Is this "source" claiming to reveal secret information about Google's being a big ad business we can't verify for ourselves and that would change our minds if we decide that he can be trusted?
Nothing of the sort. He's expressing an opinion about things that nobody disputes. Calling him a hypocrite means you don't like his opinion and think that calling him names is a good way to weaken his argument. Of course it's meaningless and defending such silliness on the grounds that this is all about the credibility of an information source is beyond silly.
