But know you are changing the situation, if it was a CRACKhead coems in and then reaches for his pocket then by all means put one in him....but if someone just gets in and expects to strongarm you but gets a gun in there race, i am pretty sure that you got control of the situation!
But not all times, will you know if he is a crackhead or some other high. That's called RISK. You never know what's in the mind of a stranger barging into your habitat. No reason to leave anything to chance. Later, QD.