"bad spots", reaction...
I disagree to a point about the bad areas or spots with trouble.
In the mid summer of 2011, I ran into a closed US Post Office on a Sun afternoon to mail a few postcards out. In the post office on the floor was a vagrant who asked me for $. This took me by surprise & the USPS office was in a "upper-middle class" suburb. Not a ghetto or "bad area".
The big issue with armed citizens & concealed carry(not sworn LE or armed professionals who know they going to around criminals) is that you must react rather than act in a critical uncident.
That's why it's so important to be well prepared & to be alert.