I think I remember the Star Wars Expanded Universe saying Palpatine hated women and aliens. I know Pellaeon mentions it in The Hand of Thrawn at least. I guess writers based this on no girls or aliens on Star Destroyers in the original trilogy. But in the prequels Palpatine is chummy with loads of aliens (Darth Maul, the blue guy in Episode 1, the Viceroy) and girls, well, girl (Padme) so I'm wondering whether GL ever spoke up about it.
No, there has never been any confirmation from George Lucas regarding Palpatine's xenophobia or chauvinism. In fact, the portrayals of Palpatine in the the prequel trilogy have encouraged a ret-conning of Palpatine as not personally prejudiced, but following policies set by his advisors. The use of a clone army also encourages a pro-human outlook.
The idea of Palpatine as xenophobic was developed primarily by Timothy Zahn in Dark Force Rising and Mist Encounter, with other EU authors adopting it. Kevin J. Anderson added the chauvinism in Jedi Search. This was done to explain the lack of aliens or women in Imperial forces in the films, which was due to budgetary and technological limitations. With those limitations gone, Lucas expanded on alien - though not greatly on female - roles in the prequel trilogy, as well as The Clone Wars.
This is not to say that there is no evidence that Palpatine was anti-alien. In the novelisation of Revenge of the Sith for example - while written by Matt Stover, Lucas had final say over the novelisation's contents - Count Dooku is revealed as being very speciesist, with a plan to recreate the Republic as an "Empire of Man." Stover may have been making an homage to Zahn's 'Dominion of Man' in the Cobra series with that quote. How many of his apprentice's views Palpatine shared is debatable, but the evidence that he was at least mildly xenophobic is there.