I'm sure they don't think exposing adultery is inherently bad, but rather that the method employed feels like an excessive violation of privacy.

If you'd like a different example, imagine a man is angry that his ex wife is with someone else now, and uses such a service to figure out where he can find the pair.

Heres a better example: want to escape an abusive relationship? Your license plate may help your abuser track you down again.

There are better ways to deal with stalkers then fighting the windmill of license plates.