Even if that crank is no good, it needs to come out of there for the engine to be used. That ugly thing needs to come off.
If you decide to cut it off, I find it is easier to cut at an angle to the crank. That way, I don't hack up the engine. Work around the crank, looking occasionally to be sure you don't cut into the crank. If you do, it will be OK as long as you don't get too deep. Then take a chisel and hammer. Whack the chisel into your cut. You may need to make a matching cut 180 degrees from the original one. That way, the sleeve will split in two and come right off.
A saw will not cut it. You will need an abrasive wheel.