I have to disagree with that person. Maybe not 18% but waitstaff rely on tips and if the service was decent why wouldn't the good Christian diner not want to tip the person anything at all? Sorry but I put myself through school waiting and relied on tips.
Attached is a Link to a copy (public information) of the Chriswell Foundation's 2016 990PF filed with the IRS in 2017. This is a Private Foundation affiliated with the First Baptist Church in downtown Dallas. This reflects just contributions received, income and assets of the Foundation, not funds and other sources of income the church brings in, most of the funds, if not all of which, are non-taxable, but reports have to be filed with the Service. Lots of this information about religious institutions' taxes on the internet. Gives you an idea of how much money the mega-churches bring in tax free. Enjoy! LINK: http://990s.foundationcenter.org/990pf_pdf_archive/237/237226473/237226473_201612_990PF.pdf