Heck, just the fact that people talk about concentration camps indicates how skewed the Western perspective on the Holocaust is. Something like 3/4th of the victims were dead before the end of 1943, and a vast number of the deaths (as well as, proportionally, most of the mass shootings) occurred in Eastern Europe in places that a lot of westerners have never heard of. Half the reason that Auschwitz is "our" vision of the Holocaust is because people actually survived going to Auschwitz (though all those death camps in Poland &c. going behind the Iron Curtain after WWII ended didn't help things either, nor did many of them being dismantled).
There's also the (partially successful) attempt by nazi apologists and hardcore anticommunists to muddy the water on who was actually responsible for most of the Eastern European massacres, with many being blamed on Stalin's Soviet Union. It doesn't help, of course, that there were many massacres that were indisputibly Soviet, and there's a reason Hitlers forces were initially welcomed as liberators, before the SS moved in and proved to be even worse than the NKVD.
@Hegoland
I've seen statements attributed to Hitler where he outright stated that he planned to deal with Poles and "Slavs" in a rather permanent manner, and a few others where it was pretty heavily implied, even before the war.
Not Peace But A Sword (published in early 1939 as a call for an immediate first strike against the Reich) presented several speeches where Jews and Poles were referred to in the same terms, and included some variant of the phrase "Jews first, then the Poles". It should be pointed out that this particular book predicted the Holocaust down to casualty totals, propaganda methods, and in a few cases
dates.