You’ve got to hand it to the activists at Oceana. Their tunnel-vision fantasy about supposed “health hazards” from traces of mercury in fish is so acute that even robust scientific evidence won’t shake them from their crusade. That’s dedication.

The group plans to protest against a major grocery chain tomorrow in Miami during the South Beach Food & Wine Festival. They’ll have leaflets, an airplane-towed banner, a giant inflatable “toxic tuna" fish, and absolutely zero credibility.

Oceana wants every grocery store in America to post mercury warning signs where fish are sold.

This goes against the judgment of the Harvard School of Public Health (“the health benefits of consuming fish… exceed the potential risks”).

It also ignores the biggest study so far connecting fish consumption during pregnancy with childhood development (the FDA & EPA fish advisory “apparently causes the harm that it was intended to prevent”).

And it completely disregards a recent caution from the Institute of Medicine that seafood warnings targeting only some Americans may actually scare all of us. (“Consumer messages should be tested to determine if there are spillover effects for segments of the population not targeted by the message.”)

We’ve summarized this evidence in a neat little report (which Oceana ought to read, but clearly hasn’t). In the meantime, grocery chains that give fish the skull-and-crossbones treatment are essentially stigmatizing a health food. And Oceana’s current Miami target has it right: “We’re in the business to educate our customers, not alarm them.”