Why? Partly because even though Hitler hated the Slavs in general as 'Untermenschen', he still regarded them as worthy of life, albeit a slave's existence. The same could not be said as regards the Jews. He also relied on the Poles hatred of Jews, after all, they were pious Catholics, much as the Spanish, the Austrians and the French.
Biased load of rubbish!!
It is well documented that Poles did not hate Jews before WW2. The Nazis target all Poles who were educated and wanted to kill all of them, the Poles were to be destroyed but used as slaves before this.
The "Final Solution" gives the game away. They didn't know what to do with all the Jews in the camps so came up with the idea of using gas to kill them in large numbers.
1943 this started. The Nazis tested using gas on the other prisoners before mass killings started.
6 million Poles of which 3 million were Polish Jews, 6 million jews of which 3 million were Polish Jews. Makes 9 million killed.
Out of the estimated 29 million civilians killed by the Nazis that is only a third!!
It was not just one race of people the Nazis wanted rid of for ever, remember that in all your arguments.