Re: People are griping about the practicality of a "light sabre"?
I think you'll find that most of the serious gripes are with the consistency within the fantasy. Or the aesthetics of this new facet of that fantasy.
i.e. a) a guard that can be sliced through with ease isn't a guard at all (the base of the guards are mechanical/metal). That's a practical objection not with reference to external practicalities but based on the established "physics" *within* the fantasy.
or b) it looks stupid (an objective opinion which by definition is neither valid nor invalid)