Am I a bad dad for using cold/cool water to wash my son from waist down when he goes potty or poo in pants?

Washing 2 1/2 yr old son with cold water from waist down. consisting of taking a glass and filling it up with cool to cold water to wash son from waist down when he goes potty or poo in his pants. I did it three times (today) and no other time. We praise him when he goes potty like he should, and he does alot, but sometimes he decides he just wants to go in his pants.. Finially I thought this would get his attention. I felt horrible doing it, but each time it only lasted a couple minutes (a coulple glasses to get him wet, apply soap, then a few more to rinse him off). I didn't get his upper torso wet ( i don't want to give him pneumonia, or traumatize him) but I did want him to learn that going bathroom in your pants would not mean a nice warm washing, but a cool to cold one. He obvoiusly screamed during the glass pouring of cold water, but that only lasted till we got him dry within a minute or two and got him dressed, then back to playing around the house with Mom,Dad, big sister, and little sister. Part of my mental anguish is that my wife's mom didn't agree (she never does however), but sometimes my wife also sort of goes along with her. So I just want some objective opinions about the matter. I am sure that after today I will do other things to try to get my son to go potty as he should (time out, withholding favorite toy, etc.), and just wanted to know others' opinions as to whether or not I was out of line (either way he had to be washed, I just didn't want to make it pleasant).