Suppose you grow grapes for a living and you believe that your grapes are better than everybody else’s grapes. In fact, you spend a lot of money branding your grapes so that people will choose your grapes, not just anybody’s grapes.
Now here comes the state telling you that you have to contribute money to some grape marketing board so that it can run a stupid generic grape advertising campaign, which in your view, sends the wrong message that grapes are grapes. Why should you be forced to pay money for a message that (1) you don’t agree with; and (2) might hurt you competitively?
Here’s a Ninth Circuit decision discussing compulsory agriculture advertising laws – thanks to How Appealing for the link.