This is excellent; I certainly hope that it is authentically from a professor at UCB.
The notion that ‘diversity’ only pertains to skin color is inherently racist. There seems to be no room for diversity of THOUGHT in academia today.
Here’s an alternative link to the letter, and some commentary on it - the letter seems to have been ‘canceled’ by the host you posted in the header:
Not cancelled, just under “investigation”. You can click through to the article at the posted link.