As we previously reported, Arenas faced a ton of backlash for going on an offensive rant on Saturday ... shortly after LeBron James and Team USA squeaked by South Sudan prior to the Olympics. Celtics legend Paul Pierce also found himself in hot water for making similar remarks during an appearance on "Undisputed."

The ex-Bulls and Lakers forward -- who serves as the president of the South Sudan Basketball Federation -- broke his silence on both Arenas and Pierce's controversial words directed at his native country's team ... saying he wasn't upset or angry by their words, but more "disappointed" it came from two former colleagues he's always respected.

"Moments like this are not for us to get upset and lash out," Deng said on Instagram. "Many Africans and Black people who embrace their African heritage are working hard to bring all Black people closer by educating and sharing stories and historic moments, teaching that we have much more in common than differences."

Deng thanked Pierce for apologizing for his comments ... but said Arenas' reaction was more "disrespectful and cruel."

"Personally, I don’t care much," Deng said. "I would never trade places with anyone; being African is special. However, for young African and African American kids who admire and listen to Gilbert, these comments can make you think less of yourself and make the rest of the world think less of Africans."

Arenas got wind of Deng's reaction ... and publicly shared his regret for the harm he caused.

"I respected u as a player and will as a coach (Sorry for my Disrespectful comments)," Arenas said.

Agent Zero even wished Deng luck in the upcoming Olympics ... but joked "not enough to win the Gold 'Silver' is all urs."