Then your laid back Lutheran Grandpa didn’t know what he was talking about. Fr4eewill Baptists wash feet in their churches. The only footwashing I’ve ever been subjected to in my Southern Baptist church building is when I shower after playing sports or working out in the family recreation center.
The term was meant as a tease—this is South Carolina and we have all kinds and grandpa had many Baptist friends—heck you can’t sling a dead cat round these parts without hittin’ one—and he would call them “footwashers” to their faces and they would joke that he was going to heck because that little sprinkle of water on his forehead when he was a baby didn’t count as a real baptism;)