In case of a "trolley problem[1]", you will not switch the track and will let the tram run over 10 workers instead of 1, because the tram is already on its way. Right?
Bandera was jailed by Nazi for almost the whole duration of the war (1941-1945). His brother was murdered in German stalag. It doesn't look like collaboration with Nazi.
Soviet Union and Germany attacked Poland together (and started WWII). It's cooperation with Nazi.
If we look at the argument often used by Russians, that X is Nazi because he collaborated with Nazi, and then apply it to Soviet Union instead of Bandera, then Russians found thousands of arguments why this is not true.
[1]: https://en.wikipedia.org/wiki/Trolley_problem