How would you handle this?

[Fedex]

I was line judge in a youth game. On one play, A's guard and tackle on my side were not set for a second before the snap. At the snap, I throw my flag. After the play, I tell my white hat that I have an illegal shift on the guard and tackle. He asked me what happened, and I told him that the guard and tackle were not set. He begins to lecture me that I need to shut this play down. He calls it a dead ball false start and doesn't give B an option. Now, I know that this is a live ball foul and he threw me under the bus on it. Luckily, the situation didn't repeat itself, but how would you have handled it if it happened again during the game? Would you again properly throw it as a live ball foul, or would you improperly shut it down as a false start (thus avoiding another scene)? My white hat in this game was an older gentleman and wouldn't buy my argument. It was pointless to argue with him. Did an illegal shift used to get shut down in years past as a false start? Thanks for any feedback!

Scott