Hitting a child is abuse. It’s inexcusable
If you don’t know the difference between “hitting / abuse” and “spanking / punishment”, then I suggest you don’t engage in spanking your children, if you have any. As other posters have stated, there is biblical support for the practice, and other people’s attempt to use the “Jesus never did it / said it” line either forget Jesus, as the 2nd person of the Trinity, was around when Proverbs was written, or they don’t realize that Jesus will institute a punishment far more severe upon your death should you die with an unforgiven mortal sin on your soul.
From a secular perspective, a good parent realizes that different approaches may be required to change behavior in your child. “Time outs” might work for one child, and may be totally ineffective for another. Likewise with spanking, it is highly effective for some kids and not effective for others. I have spanked my kids a total of about 5 times each, give or take.
My children themselves will tell you that spanking worked on them, and that they deserved it when I did it. For example, I had one child who decided to jump out of my car while it was parked at a busy gas station, and almost got hit by another car. The spanking he got conveyed a message a time out or lecture would not have. Smacking the hand of a small child getting ready to stick their finger in a light socket correlates pain with the light socket without the child actually getting electrocuted to get the message.
As for the long term effects of spanking, I can only from my perspective, spanking has contributed to my kids being exceptional young people, who are respectful of others. Both are straight A students, outstanding athletes, well adjusted, loving children who have no interpersonal issues. They are popular with their friends, and outside of two altercations with each other, they have never been in any fights. (So the argument that violence begets violence does not apply here either).
Sorry, but you opinion holds no water with me.