>Why put that on him, rather than Adam Zagajewski or Czesław Miłosz or Wisława Szymborska?

Because by 1961 the Nazis had been destroyed, so it was very much beating a dead horse, and because his country was the one that perpetrated the massacre in Poland and never owned up to it.

See the comment upthread about de facto Holocaust denial in the Soviet Union. This was an act of moral courage that Yevtushenko is justly lauded for.

This is not correct though. Holocaust was ignored or silenced due to ideology, not denied.

Not trying to say this is somehow better, but this just different. In other words Yevtushenko wasn't trying to bring to reason, but rather make sure people won't forget.

I don't think you can reproach anyone for not being a hero, and especially for not "owning up" to crimes they never committed. That said, I just listened to that poem and it appears to be a stab at Russian antisemitism much more than at Nazis. I believe by the 60s antisemitism was already an unofficial government policy in the USSR, so he's in no way beating an officially designated dead horse. Pretty sure publicly mentioning Katyn at that time and place would have been suicidal.