Like I said before, children aren't so easily damaged and a bit of physical punishment isn't going to destroy them, but it's far from the best way to discipline your child. Why should you care what experts say? Because they dedicate their lives to finding out how children develop and grow under what circumstances. It's what they do, and most people in the field are parents themselves.
Physical punishment deprives children of the opportunity to develop an internal set of moral standards. Instead of "I shouldn't do this because __________" they learn "I shouldn't do this because someone will hurt me." Obviously this isn't an all-or-nothing thing and there are many degrees of it, but it's a fact nonetheless. When children grow into adults where no one's going to spank them they're more likely to do things based on the fact that they
can rather than thinking of whether or not they really should.
Physical punishment also teaches children that violence is an acceptable way to control people. Some people think that's fine; that it's manly or acceptable to pop someone in the nose if they piss you off. Most people don't.
If you want to toss facts and loads of research right out the window that's on you, but I just think it's an ignorant thing to do. You're taking your subjective experience which you have nothing to compare to unless you've lived two seperate lives, and some superficial examples of people you know over tons and tons of research.
I probably seem angrier than I am, and for that I apologise, but to
refuse to educate youself on a topic based on some notion that you're more of an expert than experts? That's just silly.
I found an article that is, admittedly, on the extreme side, but not inaccurate, if anyone wants to read it. I'm personally really frustrated with how people don't think they need to learn anything about children before attempting to raise them, so if you plan on having children someday I recommend you at least skim it:
*link*