> Even if Russia is our worst enemy, depleting their resources first is quite a logical step. Would you want Russia to be the last country that still has oil reserves for its military?

The fallacy in this reasoning is that with the money from the sales of gas Russia can - and is continuing to - arm themselves and conquer more land and kill more people. The Qatar is not engaged in killing thousands of people right now - if they were, we would not be buying oil from them, either, for the same reasons we are reducing our dependence on Russian gas.