Misinformed guy, misinformed dad. When I was a kid, a guy in my school told me that his dad told him that just before you make it with a women you should run out of the room and whack off.
Could it be that his dad was quick on the draw and fired off his Schmeisser to early and had to resort to whacking off to control his little Gunther, then passed this bad advice on to his son.