Huh, nobody's sent me one. But why would they? They don't have any address that's even remotely relevant.
But if they did... perhaps I would return it with the invitation, "Come on back - to the wider Christian community." Come to church with me for a month or so. See what my church teaches. See what the congregation do to reach out to others, and to help the community generally. See what the Christian community in my city, comprising many denominations, does, to help not just the Christian community, but the entire city - believers or not. See how we engage with those around us. See the help, healing, deliverance available to all.
And then tell me you can do it better. Yeah, right.