Timely advice from a Southern Baptist denominational bureaucrat on dealing with "issue Christians" who show up at your church (those obsessed with Calvinism, or politics, or homeschooling, etc.):
In most cases, I've decided that "this is not the church for you" is actually the right response for "issue Christians" who are visiting the church.
when these are the primary defining issues in the first (and every other) conversation, the correct response is help them move on and do so quickly.
Simply, "issue Christians" generally do not fit in well in a mission-focused congregation.
"Issue Christians" love to debate and display their knowledge. It is not good stewardship of your time to have these debates and you are not being a good steward of your church to let them loose inside.
"Issue Christians" want a platform with you and your church because they are passionate about an issue--don't let that distract you or your church from being and doing all that God has in store. Move on... and move them on.