Police are local and FBI is federal. Defunding the police takes control away from the citizens and funding the FBI puts control in the hands of tyrants.
Most places in America have only one local police force. (Some have multiple such as village, town, county....). The places with only one local force obviously are in a different position than those with a few or several. Some places in New York State defunded their little village over some combination of expense, annoyance or corruption and things worked out fine. Defunding the NYPD would be a different matter. As for the FBI, there are scores of other large federal police forces, from the USMS to BATF to DEA to HSI / ICE to CBP to Secret Servicr to the US Park Police, I mean the list only goes on from there. Essential FBI duties could easily be shifted to other agencies. Pence is an idiot.