Bearing in mind that I am PAX not crew - guns for flight crew? No thanks. Any carrier with that policy can fly without me.
Why? You would have to KNOW that there is a problem, DRAW the weapon (from some suitably secure container not a smooth leather holster) TURN to look over your shoulder to see who it is that wants to bop you on the head. ASSESS the situation and consider who is standing beside/behind/in front of the atacker, DECIDE on action to take. Oops, they just bopped you on the head/sprayed MACE/knifed the hostie etc.
Also, we have seen many remarks about the low ebb that crew reach when they are near the end of a long sector. Let's say that you have been on duty for ten hours (since briefing) and although you have not been in the driving seat all the time, you are going to be right and ready to take the above kind of action when Mr Nasty arrives to disturb your view of the dawn.