"Mein Kampf" is only about killing Jews. That's not offensive to The Left.
I think it's silly to ban books but they are a private company, they can ban what they like. To me it looks like they are jumping on the SJW bandwagon. Mein Kampf is also historical you shouldn't ban that either if you want to undestand the history of the Nazi's. And you are wrong. It is as offensive to the Left as it is to the Right.
In 'Mein Kampf', Hitler wrote, vociferously, that Jews are perfidious, elitist, have only their own interests in mind, and should NEVER be allowed to hold any political power.
Left-leaning organizations such as BDS, Democratic Socialist of America, BLM, etc, support those same conclusions. They preach, also vociferously, that Jews should NEVER hold political power in their own state and only maintain a state by use of the same traits of which Hitler accused the Jews.
Actively working to put an end to a Jewish State in Israel puts the lives of millions of Jews in Israel and elsewhere at risk. You tell me if the people who support that are offended at the idea of killing millions of Jews.