Politics are about shared values as much as they're about anything else. As the author points out, California is completely out of step with the country, and provided Hillary Clinton with 100% of her margin of victory in the popular vote.
Of course, if we could agree to abide by the 10th Amendment there'd be no reason California should have to leave. They could live by their own values in perfect accord with their nearby neighbors' living in accordance with more traditional values.
Yet in the wake of Trump's election, I have seen no signs at all of any softening of the idea that the Federal Government Should Rule All. I have seen calls to abolish the electoral college, calls that are completely removed from the reality that Democrats now control none of the capacities that would enable them to amend the Constitution. I have seen calls to abolish the states, even though state governments like California's (and there are less than a handful of such states) provide Democrats with their only practical shelter against whatever Trump's Federal government may do.
If I were inclined to view political disagreements in medical terms, I would think this pathological. This insistence on imposing one-size-fits-all solutions on a big and diverse nation is what lost them all of those state governments. It's a major contributing factor to what lost them this Presidential election. It's also lost them a bunch of House and Senate seats. Yet they continue to double down on the strategy, determined to knock down all remaining laws between them and a fully centralized power. They do this without apparently realizing that these are load-bearing walls, and the power will be centralized like a roof being brought down on their heads.
So yes, by all means, let them go. I will gladly support any Constitutional convention or amendment aimed at freeing California to pursue its own destiny. We would all be happier, and our politics would be healthier, if we could make this happen.