It mostly just boils down to the same "perfect victim" nonsense that also manifests as "but do you condemn Hamas?" Yes Ukraine does bad things. Very bad things. It was known as the most corrupt country in Europe, a title that has fierce competition. That still doesn't justify an invasion.

And it isn't like Russia didn't invade before the 2014 coup; they actually invaded during the riots leading up to the coup, and seized territory that they still hold today (as Israel has done so many times to Palestine).

They also aren't only looking out for ethnic Russians in the Donbas. The initial invasion planned to take Kyiv, the Ukrainian capital. It turned out that the Russians significantly overestimated their capabilities and underestimated the amount of military hardware that Europe and the US were willing to offload on Ukraine.