I'll try to answer some of your questions and some of the myths and fallacies in your post (don't blame you, since they are heavily perpetuated by the anti-gun, anti-Freedom media).
On open carry vs discreet carry (also known by the misnomer "concealed carry"):
When you are attacked, you are already at a temporal disadvantage; reaction ALWAYS follows the action, so you are left trying to "catch up" to the aggressor's attack in order to defend yourself. Why give the criminal an even greater advantage by handicapping yourself with having to work around a layer of clothing covering your sidearm to simply draw it? The same applies to either an empty chamber or, MUCH WORSE, an empty chamber and an empty magazine.
Open Carry is the only way to head off such an attack (holding all other things constant, including situational awareness) by letting the criminal know "I'm not an easy target". If antis would ever watch the nature shows, they'd realize that predators TEND to (read: seemingly always) attack smaller, weaker, or injured individuals. I've never seen an attack sprung on the biggest, healthiest, strongest herbivore in the herd.
So yes, Open Carry is carrying for defense. As a matter of fact, I would say it is the ONLY defensive carry, since an unseen weapon is only advantageous as an offensive tactic (if you are the assailant), whereas OC tries to prevent the attack from ever taking place. Discreet carry leaves the carrier looking like a soft, easy target, OC tells the criminal "I'm armed, I'm not an easy target".
Unlike people in the armed forces, criminals don't generally have the "accomplish the mission at all costs" mentality. Their train of though is usually along the lines of "get in and out, but don't get caught". A firefight is the last thing they want since they might end up dead. Bad for business.
As for believing open carriers to be more dangerous to you and other law abiding citizens: a thug may need to ditch the weapon, so spending some money on a holster is not an option because of cost, and the fact that the holster would connect said thug to a particular weapon. So it is pretty safe to say that maybe an open carrier is not as dangerous as the thug whose gun you DON'T see tucked in the waistband of his underpants.