I'm not so sure this is "obvious". It presumes that those people will never refer anyone who would watch your ads, and also that search engines won't down rank you in results based on the number of people bailing from your site instantly/avoiding clicking on it.
I agree the position I suggested is only a plausible assumption rather than a self-evident truth. Even so, I think it's a reasonable premise. Most people aren't going to use an ad blocker and then immediately leave your site just because of some related message, so I don't see the search engine issue as much of a danger. You might lose a few people who might have clicked on your ads if someone hostile spreads the word around, but firstly I doubt many people are really going to do that either (do you leave a web site and then immediately post on your blog/Facebook page/Twitter feed that "Site X Sucks!!!11!", really?) and secondly even if they do then I suspect the odds of converting anyone they tell who acts on that information are very low.
