'Skyscraper' singer Demi posted a lengthy and scathing message on Twitter earlier today, warning of the dangers of internet bullying and slamming anyone who would attack a young girl from behind a computer screen.
It appears some of the nasty comments were about Madison's battle with scoliosis.
"For anyone telling me to 'chill', the impact bullies have over the internet can lead people to suicide," wrote Demi.
"I can handle the bulls**t. But do not f**k with my baby sister. I'm all for peace and spreading love UNTIL you go after a 12-year-old who did NOTHING to you.
"So disappointed that after all the conversation about cyber bullying in this world that people would continue to do this to others."
Demi then posted a message directly to her actress sister saying: "You are beautiful and the most precious little angel in my life and I will always protect you. I LOVE YOU."
She later added: "Physical disabilities are NOTHING to joke about. SEVERE SCOLIOSIS IS NOTHING TO MAKE FUN OF."
Fans of Demi and Madison were quick to voice their support online, getting the hashtags #MadisonIsBeautiful and #FeelBetterMaddie trending worldwide.
A grateful Madison tweeted: "I'm speechless. I love y'all so much. Thank you."
Demi added: "True Lovatics - GO!!!! I love you guys.. You have the power to cheer her up.. we love you."
Reveal is now on Google Plus! Join us here for the latest pictures, fashion and celebrity news!