Not a big fan of cutting anything due to the cost of reversal. You can tuck that arm down and kuryakyn makes an chrome cap for the stud.
If you decide to cut it, you push it in to expose the shaft and take a hacksaw blade, wrap some of it with electrical tape to not hurt your hand and slip it behind the inner primary and cut through the shaft. The arm comes out the back and shaft out the outside. Hole in inner gets plugged as does the outer primary. Newer primaries like your need to be plugged. Older ones had a plate you changed that eliminated the shaft hole.
If you decide to cut it, you push it in to expose the shaft and take a hacksaw blade, wrap some of it with electrical tape to not hurt your hand and slip it behind the inner primary and cut through the shaft. The arm comes out the back and shaft out the outside. Hole in inner gets plugged as does the outer primary. Newer primaries like your need to be plugged. Older ones had a plate you changed that eliminated the shaft hole.