So, Rush Limbaugh and his thundering herd think they can cause chaos in the Democratic primaries by crossing over and voting for Hillary. Actually, Democrats have a special talent for internal disorder and don't need a lot of help from outsiders.
I don't have a big problem with Republicans participating in Democrat primaries (or vice versa) where that's permitted. The rules are the rules, and overall I think we learn more from open primaries than from closed ones. Remember how Texas Democrats crossed over to vote for Ronald Reagan against Jerry Ford in 1976? There was a message in that, for sure.
If you're offended by Rush's tactics, give him a taste of his own chaos. Call in to his show. If they put you on, denounce him -- that's your right. If they don't put you on -- that's his right -- call again and again.
Or, you can just continue to ignore him. Serious folks have better things to do in this election. Let's do them.