"My sweet, smart, motivated princess @arianabiermann. She has the biggest [heart] and is even more beautiful on the inside," she wrote. "And you LOW LIFE a**holes who have the audacity to make your rude comments."
Referencing some of the things said about Biermann on social media, Zolciak continued, "'She finally lost weight. She finally came into her own.' WTF is wrong with you! You are the problem with society."
The 37-year-old didn't stop there. "What possesses you to sit behind a computer and write a negative comment?!!!!" she added. "Can you imagine if you took the time to write something positive or nothing at all? How wonderful this world would be!!!"
Zolciak ended her lengthy caption with a warning to her 1.3 million Instagram followers. "You leave my baby alone, she is a child!!!! Got it!!!"
"I don't know Kim personally," Zolciak said of the reality star. "I do know her sister Kyle, and I adore her. I don't know the whole story and I definitely don't feel like I'm in a position to comment, I just know the toll being on any Housewife franchise can take on you. It's difficult."