I think that there is a happy medium that can be reached.
I was smacked as a child, don't know when, but it stopped when i was 10, my sister was the same, but lucky ***** got to stop 2 years earlier because my parents didn't want to do it to one and not the other. The physical discipline i experienced was only in extreme cases, and always when my parents had exhausted all other options, so we knew when we got hit, we fucking deserved it.
The difference between what i experienced was i was not beaten, it was one hard (for the time, probably not now) hit on a ass and told to get to my room, i was never hit more than that and that one hit made me stop whatever it is i was doing.
I am a parent now, and i smack my child, never even hard enough to hurt, and only if i have tried all the other tools i have, and trust me, i was unemployed for a year, back when decent internet was not around where i live, i have watched enough daytime crap like Oprah and Dr Phil to have a huge arsenal of alternatives, and it is used as a "now daddy has had enough and this behavior ends now" thing rather than a "I'm going to kick your ass for doing that" sort of thing.
Basically what i am saying is that, if it is used as a last resort, not intending to inflict "bad" pain and is used in conjunction with something else (i always turn her back around and explain what she did and why she got smacked), especially for a 5 year old, it can be a game changer. She isn't scared of me, there are no tears except when she knows she is in trouble, cos her mum caves when she cries, and 1 minute after she has stopped the bad behavior and we are back to playing or whatever.
So yeah, smacking is ok in some circumstances, and only if it is used right, beating on the other hand, not ok, im not religious at all and i hope those people rot in a special kind of hell
EDIT: I just want to make sure i am clear, i do not beat my child, she is never injured, cries from pain or is afraid of me, even the threat of violence doesn't scare her, if i say "im gonna smack you" she laughs and points her ass at me, just to be clear, not child abuse, last resort disipline