Daycare, for sure. He pays them to WATCH the kid, not to potty train him...that seems to be what the dad wants them to do. Maybe not, but the comment on how he was angry the daycare didn't want to continue potty training at this time makes it seem like he feels they are supposed to help train him...and that's not right. That's not their job.
Plus, it IS unsanitary. Not only for the other children but for the employees as well. I mean, yes accidents are going to happen in that setting and everyone knows it and how to handle it. Unless they have one employee per child, they don't have time to constantly watch one kid to see if he stands differently or not.