How to kill (the concept of) God
1 - conceive something omnipotent;
2 - if it is omnipotent, it can lie;
3 - if it can lie, we can not say with certainty what it can or cannot do;
So, we arrived at a contradiction of items 1 and 3. So, the concept of something being omnipotent is self contradictory.
I think the argument would be that if something is omnipotent, it wouldn't have to lie.
One thing not necessarily follows the other. In fact, there is nothing that God needs, or has to do.