It has nothing to do with people thinking they're "perfect parents" by advising no spanking and offering other suggestions. If that's what you take away from it then you're missing the point. If you're seeing judgment in suggestions that are valid, you're missing the point.
I have a very spirited ADHD, ODD eldest child. She has always been very verbally defiant and is one of the biggest challenges in personality I have ever met. I do not hit her. It's not effective. She is so sensitive that she would crumble upon being hit.
I have a "perfect" child in my youngest. Hitting her would break her spirit.
My middle child is autistic. That brings along a whole separate set of issues that are unlike most that ANY of you have ever seen. Hitting her even with a slight slap is akin to beating her due to Sensory Processing Disorder.
My children aren't aggressive because of their discipline. They know what the consequences would be. There has been running commentary since they first started swatting as babies over the fact that hitting is not acceptable. It's non-negotiable. They know this, and they accept this. They know that there will be unpleasant consequences... and they don't have to be hit in order to be unpleasant.
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He doesn't need to understand what he did.
"We do not hit." Issue a consequence that has immediate meaning and effect. You do this each and every time he does something to harm someone else physically aggressive or even verbally aggressive.
"We do not ____." + consequence.
Have the consequences established ahead of time so that you're not trying to think of something on the spur of the moment.
"If you hit/kick/push/_____ whatever unwanted behavior again then you will be _____." or ".... then you will not be allowed to _____." And follow through immediately when he does the unwanted thing.
If you threaten a disciplinary tactic, you have to follow through with it. If you don't think you can follow through then don't make the threat. Don't threaten anything extreme. Don't threaten something that ends up punishing yourself, like missing an important family function. Don't threaten things that have to do with birthdays or holidays if you can help it. Because if you do, you still have to follow through.
Screw the whole, "I ran over to my son who was now in my husbands arms and calmly talked to him about using our words and never our hands" thing. That is a running discussion and you bet he knew not to do it already. That conversation is for telling him why he's being disciplined and asking him to explain why he was just disciplined. The immediate apology was appropriate whether he meant it or not. Likely not.
It is NOT normal toddler behavior. Most toddlers are NOT that aggressive. However, I don't think he needs some sort of diagnosis. He just needs a really firm hand.
Have you considered removing synthetic food dyes and high fructose corn syrup from his diet? Things like Red 40 and other artificial colors can have really dramatic effects on childrens' behavior and moods... especially GMO foods. Our children are sensitive to these things, some much more than others, and the sensitivities show up as behavioral and emotional disturbances and problems.