MOX fuel is being used as a bogeyman to scare people. First, it is only about 7% Pu when fabricated. Almost all of that Pu is burned up during the fuel cycle. You end up with about as much Pu as you would with ordinary uranium oxide fuel at the end of a fuel cycle.
Fuel type isn't terribly important in the source term for a LWR accident. Fission product spectrum is. Why? Because that is what is released in a fuel damage event. The fuel particles themselves lack the stored energy necessary to drive them out into the environment. Cladding damage releases noble gases which are chemically non-reactive, and volatile elements like iodine, cesium, and some strontium. The fission product spectrum for MOX fuel is essentially identical to that of ordinary uranium oxide fuel. So the source terms are essentially equal.
You’re injecting profound knowledge and rationality into the discussion. Is this allowed?