NATO has literally been expanding and invading countries for decades. Yugoslavia, Libya, Afghanistan, and Syria are just few examples. In fact, US currently occupies a larger portion of Syria than Russia is of Ukraine. Claiming that NATO is a defensive alliance is the height of intellectual dishonesty.

And let's just look at a few facts about Crimea from a US government study. First thing to note is that it was never part of Ukraine proper. US government referred to it as the Autonomous Republic of Crimea. Second thing to note is that majority of the people in Crimea do not consider themselves Ukrainian, and the biggest demographic considers themselves Russian:

NATO is a purely defensive alliance, not a battering ram.

You can definitely see how this isn't true, right? It'd be incredibly problematic to be opposed by NATO and to have NATO creep up to your borders. Superpowers flipped their shit over stuff like this in the cold war all the time. It's not any different today.