What bad things could happens if Bitcoind RPC is public?
Recently ELectrum had that bug, First of all, if your wallet were not encrypted you will lose your funds and that is the most dangerous thing might happen. 

If safe mode is enabled disablesafemode=1 You will avoid any danger RPC Calls. 


  Safe mode is a feature that disables a subset of RPC calls - mostly
  related to the wallet and sending.


If you want to make your server public, Enable safe mode and disable wallet access.