My impression was after the war ended (1945) and the concentration camps were discovered - is when Nazi’s were seen (globally) as a racist/prejudice.
I have previously addressed Did people in the West know about the Holocaust while it was happening?, with thanks to /u/Estherke, /u/PeculiarLeah, /u/kieslowskifan et al. It is focused mostly on awareness of the concentration camps before 1945, but also other aspects of the Nazi project.