I'd like to say that, from my cursory experience here, Easy seems to have great judgement, so I know his impression of the situation is accurate!
In other cases, I appreciate people who are willing to say something, when something needs to be said. It is true that most of the time this practice isn't worth the potential consequences, but if we reserve enforcement and commentary to the police and any divinely-anointed profits, I think we enable society's devolution, and give a false definition to what governance itself is. At least in America, the law is supposed to represent the will and authority of the people, which can also be expressed on the sidewalk (within reason) as well as in the courthouse.
It is (of course) often hard to respond gracefully, in accord to the offense itself, when emotions get into the picture. For me, I find that I often either surrender responding at all, or overreact when I do respond. (Similar perhaps to my posts here on Rennteam!) Though I try with all my worth, I fail often. I think more experience in responding will help temper my reaction, and improve my abilities there. Hope so anyway. Well, maybe...
All that said, I think its always best to make a reasonable statement, and avoid dropping F-bombs or punching someone in the throat whenever possible. RC's example is particularly out of scale because a punch in the throat can be life-ending, and that is way out of scale with the offense he cited, though I do believe a solid response is clearly called for there, and I would have replied with some amount of severity (hopefully more reasonable, but maybe not...)
I wanted to add another thought here too. Telling someone in an insulting way to shut off their engine off for environmental reasons (if that was his point) is redonkulous and particularly unreasonable. Making a polite suggestion is all the more that needs to be done. This respects the other person's autonomy, and seems (to me) to be all that is necessary regarding the impact on the immediate environment, in general. Not everyone gains the maturity necessary to let go at a reasonable level though! And those who do come by it honestly, through practice.
I do see a lot of lazy people (assumption on my part I admit) who leave their vehicles run without consideration for children nearby, and other dangerous hazards if the vehicle should get inadvertently knocked into gear, or have some other serious problem with no one around. And that frustrates me to the point of making a statement. I was raised with bad automotive habits like these, and have slowly come to recognize them for what they are, and try to change my ways. I could be wrong about my assumption, so a polite comment suffices, and if I am wrong then hopefully we are both better off for the discussion. Hopefully...
Locking the doors helps mitigate these hazards. Leaving small children in the car while it runs (including warming the car up in the winter) is absolutely ridiculous, and when I see it, I either intervene, or at least standby to help with rescue operations when they are called for.