It's certainly illegal to hold Nazi material/signs etc etc in Germany, last time I checked at least. Least to say people are very sensitive about it in Germany, and I see no real reason to blame them for being so.
Also Hitler brought total and very obvious destruction to Germany by 1945, despite earlier success (though the same can be said of Napoleon-by 1815 France was bankrupt and a second class power)
Another reason for including Stalin and not Hitler, despite Stalin being more brutal is that Stalin was on our (US/UK) side in WW2, and so is not, in general, so infamous, particularly among those who perhaps do not know or are not interested in the subject.
I can't explain Mao's inclusion. Even more so why is he Protective?????????????
On principle I see no reason no to include mass killers in games from history since noone is sensitive to their actions anymore. Regarding Mao, Stalin and Hitler, people are understandably very sensitive about some of the attrocities commited by these people.
I'd replace:
Brennus with Vercingetorix
Hatshepsut with Tutmoses (forgot which one)
Isabella with El Cid (perhaps)
Louis XIV with Charlesmagne
Frederick with Barbarossa