"Aggressor and defender" is just not a good framework for understanding any conflict. For example, during the Vietnam War, where the US was sending troops halfway around the globe to terrorize a bunch of poor rice farmers into submission so that they could keep exploiting them, they justified it by saying they were just "defending" the state of South Vietnam.
The same can be said of either side in Ukraine. The West is just "defending" the government which they hand-picked during Euromaidan, while Russia is just "defending" the separatist governments who requested their aid. It's trivially easy to paint virtually any side in any conflict as merely "defending." Even the Roman Empire, while they were expanding across Europe, often claimed that they were simply "defending their allies." Look at an area you want to control, pick one side in that area to be your ally, wait for a conflict to break out, then use the excuse to move in, and the next thing you know you've conquered the known world, "defending" all the while.
In any case, I can't say I'm particularly invested in upholding a status quo where my enemies are the ones on top. That's their problem, not mine.