Tough one. Speaking as a parent who has raised three to adulthood and is raising a 4th, and as one who has worked with teenagers for the last 25 years, I'm hard pressed to condone hitting kids. To me it means the parenting is reactive instead of proactive. My wife and I debated it a long time when we had our first. I was more apt to think it was a solution. She was against it. In the end we put our energy into being proactive and didn't have to resort to that.
It doesn't mean the 'threat' of what might happen if Dad got mad wasn't there. But anger was something that rarely showed itself as a parent so that when it it make an appearance, it got the response intended. I've been told since that my kids referred to it as the "Darth Vader" voice behind my back.