The ASA (Advertising Standards Authority) is the place to go when you see advertising that is problematic, scientifically or factually incorrect. Their Privacy Policy makes it clear that you are required to provide your name, address, e-mail and phone number. This contact information will be passed to the Advertiser.
In the vast majority of cases this would be fine. But what if you consider the Advertiser to be mixed up with a fringe group that uses FUD (Fear, uncertainty and doubt) as their primary tool to influence people? And you also consider that some of the supporters are quite likely irrational and not entirely mentally stable? Would you want your personal address passed on to this Advertiser?
This is the position I find myself in.