as said above, tape both sides of where your going to cut before you cut it.
try and get the tape as tight round the hose as possible, should cut alright then.
use a fine toothed hack saw blade if you ca as well so it dont grab at the metal.

if its still bad then turn the blade round in the hack saw so that it is actually cutting when your drawing the saw back towards you. that will help reduce the blade snagging the metal and bending it.