I don't expect Wagner is going to perpetrate the same atrocities in Russia that they have everywhere else, so I'm happy they're going the fuckl home. That's the difference between having moral principles (invading sovereign nations is bad, murdering their civilians and torturing PoWs is bad) and picking sides. If, like DC Draino, you don't have moral principles then this is harder to handle. DC Draino there has previously been a big fan of both Wagner and Putin, but since he doesn't display moral principles he's not confused that two parts of his "side" are fighting. He can't parse whats happening through a moral lens.
Here's another example. The Nazis were bad in WWII. The US was also interning its citizens, particularly Japanese citizens, and this is also bad. When I read a history book I can still cheer for D-Day because it was a step toward ending the reich's imperialist ambitions and the wholesale murder of people in their internment camps. because I'm approaching this from moral principles rather than blind team sports, I can both acknowledge that the US did some real heinous stuff to its people while also acknowledging that the US was a vital part of stopping even worse genocides abroad.
It takes a little bit of work but in the long run being able to understand that nobody is blameless and perfect in war while also being able to assess whether there is a larger moral good at stake is a more mature approach that trying to assign people to the categories of good and evil like a child's cartoon.