Unitarians, how do you handle the Evangelical Christians who infiltrate the church?

I am basically an agnostic and joined up with the Unitarian church because they believe in everything and the women I meet there there still like to smoke pot and have . However, the pastor says she can't really stop the Christians who joined up to try to convert the "believers in God or whatever you want to call him." Any ideas on how to get rid of or shut up these Christians while they are in the church or at church functions? We don't mind at all them being Christian...would just like them to keep it to their selves.