Aaron Carter Beefs with PETA After Org Calls Out Mom Slapping Dog

Aaron Carter's mom was caught on video brutally smacking one of his dogs ... and now the singer is at war with PETA.

Aaron is trading blows the animal org after it called out Aaron and his mother, saying, "Dogs are family -- not for IG likes. SLAPPING them or SELLING THEM for a profit when millions are homeless in shelters is cruelty."

The whole incident went down Wednesday night while Aaron was on Instagram Live as he and his mom were driving across the state. At one point, you can see the pug make its way onto the middle console from the back seat when, out of nowhere, Jane violently slaps the dog ... sending it to the backseat.

After PETA put Aaron on blast, the singer responded with an expletive-laced tirade saying, "My message is f*** you, PETA. F*** you, PETA. F*** you, PETA. Whoever is running your f***ing organizations and campaigns, you can f***ing suck my d***." Classy.

Aaron -- who was briefly hospitalized the day after the dog-slapping incident -- also threatened, "I'm gonna sue the s*** out of PETA. I'm gonna take htem for millions of dollars, and then I'm gonna give back money to a community that actually does help animals."