By all means, let them go.
No for e. No threats. No violence. Just let them go.
Trump will never put up with a seccession of states. He will hold the Union together like his idol, Lincoln. If they leave the union, they will have a fight on their hands. How many will pick up rifles to defend California from Trump? Far too few I believe. Facing a draft, how many illegals will stay to fight for an independent Pacifica? How many rioting college kids will join a Pacifican Army to meet Trump Federal Forces on the battlefield? Few indeed. The Civil War will be short indeed.