Obviously, what Linden is saying in this case is probably not helping his business case. It's clear to me that he either does not understand why Maciej doesn't want to implement a private API, or does not wish to understand it.
On the other hand, neither of those things are grounds for a downvote, I think. A downvote says "this content shouldn't be on HN" -- that there's something about a comment that detracts from how the community operates. Linden has been completely respectful in what he says and how he says it. Maybe that's not the case in what he's asking his users to do, but we may as well let him ask.