Rojo,
I'd like to shed some light on this topic.
First of all, US Border Patrol is completely seperate from US Customs & Border Protection (CBP), although they are both under the Dept of Homeland Security (DHS) umbrella. When you attempt to drive across the border from Canada into the US and arrive at a CBP Port of Entry, that PoE is run by CBP, not Border Patrol. So the "guy in the booth" or the guy who looks at your passport when you arrive at the port is a CBP officer.
The information you received from the officer is indicative of their standard process. The officer told you that there is another Robert Johnson who IS considered armed and dangerous. So, once they realize (with the help of their computer systems) that you MIGHT be the Robert Johnson who is armed and dangerous, they don't take any chances. Their first priority at that point is to preserve your safety, the safety of other travelers, and the officers' safety. That's why all the other officers came running out--it's their standard process, and they acted to protect everyone's safety.
Let's say you were indeed the criminal Robert Johnson. In that case, they certainly don't want to waste 30 seconds looking at your passport and then their computer screens to make SURE you're the criminal and not the benevolent version of yourself. In that amount of time, the malevolent RoJo could have drawn a weapon, accelerated through the gate, or committed some other violent act. The point is that they recognize that you MIGHT be him, so they act quickly and decisively to preserve the everyone's safety (including your own).
I can't say whether this would help you avoid the situation that occurred recently or not, but if you're planning on driving across the border with any level of regularity, you may want to consider enrolling in their trusted traveler program by acquiring a NEXUS card.
http://www.cbp.gov/xp/cgov/travel/trusted_traveler/nexus_prog/