I don't fully understand what specifically do you mean by saying that there was no holocaust to non-Jewish Poles, but thousands of them died in concentration camps all around territories occupied by Germans and often shared identical fate to those who were of Jewish origin.
If I understood you correctly, you use term "holocaust" to describe mass extermination of Jews and Jews only, and as long as you acknowledge there's been other mass killings during the war, I'm completely fine with that.
e: it's not how I was taught history at school - e.g. teachers would include non-Jewish Poles, Russians, Hungarians, Romas, Sinti, and other nationalities that were sent to death camps too - I think by holocaust they basically meant death camps (regardless on who was killed in there) rather than the bigger scheme of killing all the Jews.
There was no systematic extermination of Catholic Poles. To be a Jew in occupied Europe was to be hunted. 90% of Jews in Poland were killed. You basically had to have a miracle to survive. There's very little in modern history like this.
Edit: The people trying to draw an equivalence between what happened to Jewish and non-Jewish Poles are largely aligned with right-wing, strongly Catholic Polish nationalists, and are not in and way fond of the Soviet era. This is mostly a post-Soviet phenomenon.