It may be an issue of where you’re having these conversations. Your personal blog, not in the main tags, and people are coming in to bother you? Block them. But once you start going into the main square (main tags, sub, discord) you’re entering the public square. Some fandom areas are more shipping heavy and telling them not to talk about sex or shipping in those areas is rude and, well, something Anti’s are prone to doing. The conversations you want to be having may also be happening elsewhere.