What is the ruling on opening a religious page on Facebook for da'wah (inviting to Islam) and knowledge, what are the implications of unintentional errors, what are the legitimate Shariah controls for it, and how should one deal with inappropriate responses?

You are permitted to denounce evil in offensive comments, and you will not be held accountable for unintentional errors you may make. However, you should not speak until you have ascertained the truth. When responding to a foolish person commenting on a religious post, it is obligatory to denounce the evil with wisdom and good counsel. If he does not respond and you are able to delete his objectionable words, then you are obliged to do so.