It should be very easy for you to prove that the claim is baseless.
All you have to do is find even one Prop 187 group that lists Rush as a member or a supporter. Or that he endorsed.
Take all the time you need. Maybe your fellow true believer null and void can help you find that elusive evidence.
Trying to tell Rush’s audience of anti-immigration conservatives that he was selling them pro illegal alien advocacy instead of the anti-illegal immigration position that they were actually hearing, and that some how they missed it, is a childish game, grow up.