Tonight there was a feature on the news about war graves in the Ukraine....I'm not sure I can think of any argument that would make a Putin supporter change his mind. Not in prose, poetry or song.
I was in StPetersburg about four years ago. Every Russian you talked to seem very approving of Putin. Local boy made good.

You can see the same thing with Donald Trump. There's a guy every lawyer not actually working for him - says he's in the wrong. He wasn't cheated out of the election - he lost it. Find another crime he's done, charge him with it - and he gets more funds more supporters.

Rational argument won't work. Point out that they are following a man with one ball - maybe you'll cut through. Can't do any harm, anyway.