That's not a reason to ignore the argument of a hypocrite. It is a reason not to ignore credibility as an important factor because of a misguided application of fallacies.
That is true, but this fact also considerably reduces the weight of the argument coming from him. There are several people talking either against or in favor of patents. Why would I listen to someone that is (or that I suspect to be) biased?
If you think the arguer is biased against the position being argued for, that's maybe grounds for suspicion that the reasoning is flawed in some (perhaps subtle) way—but suspicion when listening to arguments is always a good thing.
Anyway, as has been pointed out elsewhere in the comments, his position isn't actually inconsistent: it's perfectly rational for him to think that a system where all parties are equally prohibited from certain abusive actions is better for him than the system where they aren't, even if he's participated in the abuse in the past. He may very well have come to the conclusion that he loses more from the abuses of others than he gains from abuses of his own. [The "hockey-helmet" example someone gave is a good illustration, I think.]
But yes, Bezos cannot be assumed to be without self-interests. Nor can the (former) patent lawyers sitting on patent courts.