Shorten Rod Butt
I did it once with a miter saw, very slow feed, let the saw cut it. A table saw will work fine, too. You'll get less pulling and fiber stress than with using a hacksaw, as you're stressing the rod a lot less than the pressure a hacksaw would require. If you do use a hacksaw, use really light pressure and take your time.
An abrasive wheel will work great too, like a dremel.
And yeah, like zimmy said, if it's bare, wrap it with several wraps of duct tape.
I'm not a blank cutting pro, but that's how I'd do it.