GfS, nothing is more obvious when observing people argue that they indeed do repeatedly argue both sides of a principle, for whatever side suits them at the time. I see it happening over and over again, and I bet I've unwittingly done the same thing myself many a time.

That's because the human ego is not nearly as rational or fair-minded or objective as it usually loves to think it is. It really wants only one thing:

Victory!

And that is what makes both people and nations frequently irrational, unscrupulous, unfair, dangerous, and deeply hypocritical while they vociferously charge out to win their various illusory victories over one another.

As Shakespeare said, it's a lot of sound and fury, signifying nothing...nothing except the universal desire to win. If you point their inconsistencies out to them, however, they will deny it vociferously and just waste another lengthy piece of your time justifying themselves and launching further counterattacks on you, so why even bother? Frankly, it ain't worth the trouble.