Even if we tried to build the Keystone pipeline, it wouldn’t lower prices for at least five years!
I can prove I’m not dead.
The pro-drillers stated a hypothesis: that increased domestic supply would be a cushion against the terror premium. Under Trump, they were able to test that hypothesis. The real-world provided a natural experiment. Supply had been increased. Iran provided a terror event. The price of oil did not spike. Therefore, the hypothesis has not been disproven.
That's as good as it gets for any scientific theory: not yet disproven. It's unnecessary at best, and sophistry at worst, to trundle out the impossible standard of "proving a negative".
OTOH, the anti-drillers hypothesis (can't drill our way ...) has been conclusively disproven.
(-2)-(-1)= -1