TMZ Sports posted the video of the incident ... where Smith is seen unloading a bunch of violent kicks on a man who allegedly smashed his car window during the protests in L.A. this weekend.

Smith joined the "Pat McAfee Show" on Monday to give more insight into the situation ... and the NBAer admits he wishes the incident never happened in the first place.

"Granted, if he would've seen me, and seen somebody outside the car or outside the house or whatever, do I think he would've broke it? Absolutely not," Smith says.

"It was just a random act of stupidness, and I give him that. But, that ass whooping was a random act of stupidness on my behalf."

J.R. says he's supporting the peaceful protests in honor of George Floyd, but condemns the looting and vandalism.

"This man was down there for 8:46 for no reason. Literally, taking the life from him. Calling for his dead mother."

"And then, we go out here and try to represent his name in a good way and between tarnishing people's shops -- like so many people have nothing to do with the situation."

Smith continued ... "We should be able to lock arms and stand in front of somebody's store and say no this is not right. Being able to do stuff like this isn't right."

As for the moment he unloaded on the alleged vandal, Smith says he regrets how it went down.

"When it happened, I seen red. Then when I finally snapped to... I'm still disappointed with myself."

"For me, I'm 34 years old. I have 4 little girls at home. I don't want that image, regardless of the fact whether it was right or wrong, I don't want them to have that image of their dad being capable of doing that, and doing something like that."