That is true, I've thought about that. The way I see it is that if police are really are looking for something like that to pull someone over, I think that's good because who knows what someone could have in their car. I personally have nothing to hide from the police, so chances are if I am to get pulled over for no passenger mirror I'd either get a ticket (which would be my own fault) or the officer would tell me to put one on. But I get the small town cop thing, they'd probably find an excuse to pull over for scraping the air dam.
I'm not trying to convince you to do so, I'm just giving my opinion
Plus I had a coupe of your generation civic and my all around vision was a lot worse in the civic compared to my CRX