You are correct when you say that your argument is amusing. That’s all it is though…
Not at all - the logic is irrefutable, unless one of my premises is somehow flawed. Just because you (apparently) don't like the implications of it doesn't change the truth of it.
Let's look at it again:
P1: If there is something that God cannot do, then God cannot be omnipotent and all-powerful.
This is necessarily true, by the definition of "omnipotent". A being that is omnipotent can, by definition, do anything and everything it wishes. And therefore, a being that cannot do anything and everything it wishes is not omnipotent, by definition.
P2: There is something God cannot do - God cannot change his own law.
This is also true, at least according to gore3000. Gore3000 tells me that God's law cannot change. If it cannot change, God cannot change it. After all, if God could change it, then God's law would be changeable. But it isn't, so he can't.
C1: Therefore, God cannot be omnipotent and all-powerful. QED.
And this is the inescapable conclusion. There is something that God cannot do, therefore God cannot be omnipotent, by definition. The only way you can possibly refute this conclusion is to show that one or more of my premises is flawed. If you don't like the first premise, you'll have to take it up with the people who write dictionaries. If you don't like the second, take it up with gore3000.
I understand very well why you don't like it, but that doesn't change the validity of the argument. The logic is perfectly valid, and therefore if the premises are true, the conclusion must be true.
Logic can be a real b**** like that sometimes ;)