Slowpitch Infield Fly

Question
If we have a runner on First and Second, the batter hits a fly ball that goes out beyond second base. The umpire calls this infield fly and the second baseman drops the ball as well.  My runners on 1 and 2nd advance before the ball is dropped.   

The umpire calls the batter and all runners out. He said the runners must tag up on the base before running for an infield fly.  

Is this true?  I thought the runners were allowed to proceed at their own risk.  

Also, wouldnt a ball beyond second base not qualify for the infield fly rule?

Thank you for your advise.

Answer
Thanks for the question!

Once the ball is touched fair on an infield fly, the batter is out as a result of the infield fly.  Since the ball was dropped, the runners can advance at their own risk, but yes DO NOT have to tag up.

I would almost always call a ball behind second base an infield fly.  I would even call it farther into the outfield grass if there is good reason to protect offensive players (infield fly is always a judgment call).  The idea of the infield fly is to protect your players from a double or triple play.  By calling the infield fly, the umpire was doing your team a favor by preventing a double or triple play. (Of course, he negated that when he called everyone out.)  Now the tag up issue is a misapplication of playing rules and is protestable.

I hope this helps answer your question, if not please reply.