Undefeated MMA fighter Dustin Lampros has made a name for himself in the cage, but he's also fighting to get child predators off the streets -- and he's telling TMZ Sports the wildest interactions ...

They entered the property, where they found another child, a 6-year-old boy, locked in a dog cage by a zip tie. The boy had been naked, with only a blanket and pillow kept inside the cage ...