A thought experiment:
Would you say that it would have been a moral dilemma for you to ignore the person's swerving?
If so, what moral principle would you have violated if you were to have ignored the person's swerving?
Here is the reason I ask...
In order for a moral principle to be sound, it should be universal. It should apply to everyone. It's worth noting that the driver's swerving in your example had not yet produced a victim. Thus, in my mind, there is no crime. I do not subscribe to the notion of rights by charter, and thus do not equate a crime with a mere violation of a politician's arbitrary edict.
Following the idea that sound moral principles are universal, and presuming - I'm trying to save time by making an assumption. Forgive me if my assumption is incorrect - the moral principle you did not want to violate is allowing a person to endanger others, would you not agree that the same moral principle would demand that you call the cops on the following people...
- A man you know to wear glasses that gets behind the wheel without his glasses.
- A teenage boy in the drivers' seat with his eyes fixated on his stereo system rather than the road.
- A harried mother driving her SUV while turned around and yelling at her kids in the back seat.
- A cop driving his vehicle at high speeds while clearly using his hands to type on the computer with his attention diverted.
In each of these situations, other drivers and pedestrians are in potential danger, a lack of swerving notwithstanding. In fact, if we care to extend the presumed moral principle to its logical end, we can argue that anyone who gets behind the wheel of a huge hunk of metal and hurtles that heap down the road at 55 mph toward others places others in potential danger.
In fact, if we wish to prevent any human from causing harm to any other human, why not simply shackle everybody to the floor?
Here's my point... to repeat, moral principles must be universal in that they must apply to everyone. To be sure, it may feel as if you're doing the right thing - whatever that means, since people seldom equate "doing the right thing" to true universal and logically-consistent moral principles - by calling the cops on someone you presume would have maimed or killed someone.
But I see an inconsistency in the action. Moreover, I see the action as violating a moral principle I personally hold: non-aggression, or first-use of violence, against anyone.
Note that with the above, I'm not actually focusing on whether it is right or wrong to call the cops. That's a different discussion I'd like to avoid for now. Rather, I'm explaining the reason a decision to not do so presents no moral dilemma for me.
Incidentally, I have no intention of going back and forth on this stuff. I have watched others with more talent, smarts, and patience do so without making a major breakthrough. Any hope I might have of accomplishing more would be unreasonable.
Having said that, I thought it important to try to explain - at least, on the surface; this stuff goes deep, a fact to which any student of philosophy can attest - why my not calling the cops presents no moral dilemma for me.
Your mileage may vary.