The billionaires’ attack on the wealth tax initiative shows why it’s needed.As is the case with most election cycles, the claims and counterclaims about the ballot measures being voted on in California this time around are largely based on caricatures of the measures themselves. That’s especially true of the highest-profile measure, Proposition 40 — the California billionaire tax.What’s indisputable is that this is a “wealth tax.” It’s a one-time 5% levy on assets owned by Californians with more than $1 billion in net worth. That’s a departure from conventional state personal tax, which is levied on income such as wages...