"to ask each driver to submit to a search. If any refused, that would have been probable cause."
Really?
If I were driving, got stopped with a line of cars, and a policeman came to my window and told me that they were looking for a guy who just robbed a bank, and asked if they could search my car, I'd have no problem with it at all. To have a problem is suspect. The Bible backs me up on this one, too. "The wicked flee when no man persueth".
Under our law, it's probable cause to search a car for almost any reason. Some could even argue that the fact that there was a bank robber reported in that line would be probable cause. When I was in college, I was riding in a car with 3 other college buddies. We got pulled over for speeding, and when the police officer saw that there were 4 college aged males in the vehicle, she called in backup. 4 squad cars showed up, as well as a drug dog. They patted us down and had the dog sniff the car. Out of curiosity, I looked it up, and that fell under probable cause.
Again, I'll stand by what I said about the handcuffs being too much under the constitution. I won't say it was wrong in a moral sense; in fact prudent. It assured that the bank robber wouldn't get away. However, it was outside the realm of the constitution, and so was illegal.
When a civilian enters a military post, their car is searched. The passengers must get out and open all the doors and trunk. It's not a very intrusive search, as the guards just look inside. They don't actually put their hands on the car. This is accepted. However, when a line of cars needs to be searched to find a bank robber reported in the line of cars (a much higher probability than a civilian vehicle containing a threat), people scream out in protest.
Police officers get zero love. "Protect me; but don't worry about protecting the rest of the population if it's going to inconvenience me."