I would never cut the wires, you can just remove the pin from the connector by sliding a knife under the plastic clip. THen slide the red wire out.

In my heli, I left the red wire on the ESC and BEC... Since they are both set to 5 volts, I have a redundant power system. If either dies, then I should still have a few Amps of 5 volts to power the servos. The ESC's BEC couldn't supply enough current for all the servos under load, but it'll work long enough to get her down.

If you have the CC BEC set to 6V, and the ESC BEC is not able to supply 6V, then you should remove the red wire.