When it comes to persuading us that what is bad for us is good for us, advertisers are not novices. From fast food to fashion fads, from ice cream to idleness – we buy them all. They're generally much less successful at persuading us that what is good for us is good for us — goody-two-shoes public service campaigns haven't yet wiped out smoking, made us more energy efficient or got the masses eating five veggies a day.

But what happens when advertisers try to persuade us that something bad for us is bad for us? Ask Das Comitee, a German ad agency. It is being pilloried for an ad portraying HIV (Bad Virus that kills a lot of people) as Hitler (Bad Person that kills a lot of people). Aids groups are up in arms because they believe the ad suggests that people with a Bad Virus must be Bad People. They have unwittingly put their finger on the central dilemma of public health advertising in today's touchy-feely, not-my-fault world – how do you try to prevent something that you are simultaneously trying to normalise?

If there's absolutely nothing wrong with having Aids (or with being hugely fat, or addicted to cocaine), then why should we bother with prevention messages? If there is something bad about Aids (or obesity, or a £200-a-day coke habit), then what's so terrible about portraying it as something bad?

Aids industry dinosaurs like myself, people who have been around long enough to remember Aids, know that Aids really is something bad. What we're not so good at admitting is that it is practically non-existent in rich countries. We still mechanically churn out "the virus that causes Aids" after every mention of HIV, and we mention HIV a lot, because new infections are on the rise in gay men across the industrial world. But these days it is simply not true to call HIV "the virus that causes Aids" as if the progression were inevitable. Treatment readily available in Germany and the UK means you can have HIV without getting Aids for decades, maybe for ever. And the treatment is free for patients, if not for the taxpayers who support the health system.

I find the German ad pretty tasteless and rather unbelievable (surely that beauty in the ad could snag a better-looking lover...?) But I object to the ad mainly because it keeps dinosaur thinking alive. "Aids is a mass murderer" thunders the ad. "Protect yourself." Fewer than 500 people died of Aids in Germany in 2007 – hardly a match for Hitler. Most people of the Beauty's actor's age will never see Aids. In fact most women like the beauty in the ad aren't at risk. Almost all sexual transmission of HIV in white communities in western Europe is between men who have anal sex. Targeting straight women is not going to reduce the risk of HIV in gay men.

One of the reasons Das Comitee spent unpaid time on the campaign is because it wanted to put Aids back on the map. But should it really be on the map? HIV should be, certainly. But HIV is no longer a mass murderer in rich countries. It is an inconvenient disease that will have you taking pills for the rest of your life, cost taxpayers lots of money and make big pharma rich. "HIV increases your tax bills. Protect yourself!" Not really a line that will get you reaching for the condoms, is it?