Good exists - a Catholic comments

[Bucky Ball]

You're doubting the applicability or accuracy of modal logic here, not Plantinga or his argument in particular.  A legitimate concern, but one that falls under the "non obvious".  Do you really want to try to justify your use of logic?  Go ahead.  Justify your use of logic to call into question someone else's use of logic.  That might actually be sound, but it certainly won't be valid.

I don't have to justify anything. HE USED modal logic, I used no logic. He has to justify what he did. 
I did nothing. I have to justify nothing. Without his justifying his particular use of logic, (there are many logics) I can dismiss his bs with no further explanation.