This obsession with "moral standing" is ludicrous. Do you think the British Empire had heap loads of moral standing on September 1, 1939? Do you think the US and the USSR had barrels of "moral standing" hanging around when they joined the fight against the Nazis?
Nations do shit things, sometimes for perceived benefit, or simply out of greed. If we allowed every ill actions we had done in the past hold us back, no one would ever intervene when some other nation state violated the general rules of international conduct?
Russia signed an agreement in the 1990s guaranteeing Ukraine's territorial integrity in exchange for Ukraine's nuclear stockpiles. Thus, even excluding any notions of territorial integrity that have been a part of international law since the end of WWII, Russia is in violation of its own treaty with Ukraine.
So yes, it sucks ass that the US invaded Iraq, but do you seriously want the US to sit in the corner and refuse to come out when Russia starts enlarging itself with trumped up referendums, because a decade ago it did a naughty thing?