There are tools for removing them, but who has the time for that?
I just use a small flat head screwdriver (jeweler) inserted into the slots on either side of each pin. Insert the screwdriver into one slot at a time and pry inward (toward the pin) to flatten the barbs.
This applies to the main connector.
For the other smaller bulb connectors/sockets, I just cut the wires close to the connector and solder on new wires, covering the joint
and any exposed wiring left on the connector with heat shrink tubing.