Hornady 75gr TAP and Speer Gold Dot 64gr JSP are both currently offered as factory .223 Remington and 5.56x45mm NATO. The velocity difference can be as little as +/-50fps, depending on the gun/lot.
I issue both 5.56 and .223 duty and practice ammunition at my department. One of the best patrol rifle rounds out there (Federal Bonded Tactical 62gr JSP, as used by DEA) is available only in .223.
I have not seen anything supporting .223 being less accurate in general in a 5.56 chambered rifle. Improper combinations of barrel length/twist and bullet weight/type are much more likely to cause unacceptable accuracy in my experience.
Singled out, and called to arms to defend what they hold dearest, the number of truly evil people would be small. The number of truly good people, even smaller....those too afraid, too weak or too ill-prepared to fight would be countless.