Calexit would take the country's racial demographics back 15 years. The US' racial demographic breakdown as of 2015 as a whole/without California (Calexit change):
White (non-Hispanic) -- 61.6%/64.9% (+3.3)
Black -- 13.3%/14.2% (+0.9)
Hispanic -- 17.6%/14.7% (-2.9)
Asian -- 5.6%/4.3% (-1.3)
Other -- 1.9%/1.9% (0.0)
Not only does this take us back about a decade-and-a-half in terms of the racial distribution of the country, it also takes the total population back by about the same period of time.
Put in another way, in the last 15 years we've added the contemporary population of the state of California into the US! Another California has been glommed onto the country since Bush-v-Gore.
The country is too linguistically, ethnically, religiously, culturally, economically, racially, morally, and geographically divided to make sense as a single political entity. And there are simply far too many people for it to work. Increasingly the only argument in favor of holding the thing together is a mix of complacency and economic expediency.
A SurveyUSA poll conducted in November showed Californians opposing Calexit 57%-23%, with 20% unsure. That's a high mountain to climb, but with three years' of lead time it's not an insurmountable one. Hispanics are more supportive of it than any other group is, so it already enjoys the Diversity! seal of approval.
Speaking of Californians, the majority of those who voted for the wicked witch think Trump voters are indeed deplorable. Among Hillary voters who were asked if they thought Trump voters were good people or bad people, the distribution is as follows:
Good -- 27%
Bad -- 47%
Not sure -- 26%
It gets even better when the deplorability is put in precise terms. When Hillary voters are asked if Trump voters are racist:
Yes -- 65%
No -- 16%
Not sure -- 19%
Yes -- 61%
No -- 18%
Not sure -- 22%