It is bullshit because it only works in theory, the big refrigerator will crush the tiny fly ... in reality the fly escapes with ease the bullshit part refers

It is bullshit because it only works in theory, the big refrigerator will crush the tiny fly ... in reality the fly escapes with ease the bullshit part refers to just that, pretending that the refrigerator could be an appropriate good solution, when in fact can't actually even perform the task