Some poor excuse for a human performed a savage act on a foster dog … stabbing and beating it purely out of vengeance, and now others are mobilizing to save the dog and find the scumbags who left it for dead.

Kari Whitman, the founder of the dog rescue org Ace of Hearts, tells TMZ … a 9-year-old Dogo Argentino mix named Brodie had been under foster care in California City, about 2 hours northeast of L.A.

We’re told late Tuesday night … the foster mom, who had been living with her sister, got into an argument with her sister and at some point, Brodie was left in the yard of the home.

Sadly, when the foster mom returned she found Brodie with a stab wound down his spine, a broken leg and his hip was shattered in 4 places. Poor Brodie had previously been at a high-kill shelter before being rescued by Ace of Hearts … and at this point, it’s unclear who took out their anger on him.

However, the foster mom believes one of her sister’s friends may have done it to get back at the foster mom for the argument.

Either way … Brodie was taken to a local vet and later transferred to ACCESS Specialty Animal Hospitals in the San Fernando Valley. We’re told he’s currently fighting for his life there … and sadly, may never walk again because he suffered major nerve damage.

Kari, whose org had been caring for Brodie before he went into the foster home, tells us anyone who wants to help Brodie can call ACCESS directly and donate.

As for the alleged perpetrators … law enforcement sources tell TMZ animal control has taken a report and opened an investigation, and it’s also been in touch with cops in California City.