Certainly there are less infamous sources, but once I found it, it wouldn't leave me alone, and it seemed very apropos for this particular fic.
So trivializing the death and suffering of millions of people is appropriate for your fic? If there are other sources, then WHY did you not use any of them? You made a conscious decision to use a quote from Hitler and now you seem SURPRISED that that provokes a negative reaction? SERIOUSLY?
I'm not sure what you mean about "having Snarry associated with Hitler makes me uncomfortable," but I'm sorry it did.
That you can so easily disregard their deaths that happened barely more than a century ago worries me, to say the least. Just because it did not affect your country as dramatically as the rest of the world does not make it okay for you to use it to be edgy.
I'm not sure I had an intention in using the quote, other than that it fit the fic and hopefully gave the reader a little nudge in the direction of "everybody here is lying."
Your attitude and that you seriously seem to think that this would pass without offending anyone, even though Hitler is one of the most negatively charged figures of recent history, and quoting him LIGHTLY reflects poorly on yourself and your story.