weak Christians and demons

This was written on the chalk board at the front of the church we visited today. In case you cant quite read it, 

"Welcome to Baptist Church Fellowship of Zambia. We don't have any choice to receive any weak members who want to join us. Don't worry about if we pray for a person who have an demon in his or her heart". 

Not exactly sure the intended purpose of the writing but it does seem apparent these people know what a weak Christian is and that demons are a common part of life for them.