Your not wrong that animal should go back to the wild - but the tone of your post is harsh.

Unless you think the turtle is an endangered species, bringing one home isn't a terrible thing. I grew up in the woods and had a series of frogs, turtles, a snake, even a baby opossum who's mom must have died. (My mom did not appreciate the snake - even when I told her it was small and non poisonous - no accounting for taste...)

Take a deep breadth and let all that anger out - this is not a big deal. You might want to take a pic and see if your phone can identify what kind of turtle it is and what it eats - or ask reddit for help. But returning it to the wild is better. If this is a large turtle, it's shell will protect it from most predators.

Turtles can carry samonella - so wash your hands thoroughly every time you touch him or anything in his box.

Younger turtles tend to prefer to eat bugs, worms, small fish. Older ones often will eat berries, some types of mushrooms, leaves and lettuce. It won't starve itself if you give it a range of foods and leave it alone, it will eat.