That's something only you can decide without seeing the plant. I remove infected leaflets rather than the entire leaf branch and leave the healthy leaflets alone.

I assume you are also treating the plant with a fungicide? If not then it is just going to continue to spread faster on the plant from the infected leaflets that are left on it.

Dave

spray and pray ;)
do what Dave suggest and get yourself a bottle of neem oil extract after performing the surgery.

Thanks Dave and stevie.