"Remember, to confront him is not just an attempt to change or enlighten him. I agree that he is probably a hopeless case. To address his sexism is also a declaration to everyone else reading, as a Christian, that you do not condone his position.
Your silence translates as tacit approval."
Only because you choose to interpret it that way. I don't know about you, but I have a job and a household and I have much more important things to do than run around on every site on the internet and denouncing every single uneducated comment some Christian makes. The only person responsible for his comments is his own self.
Further, I'd hardly call this last 10 posts "silence".