How much does a conflict of interest weigh?

Recently I read two studies on mercury, one by the New England Journal of Medicine about the neurological effects of Thimerosal in vaccines, another one by Environmental Health Perspectives about dental amalgam that concludes that boys do not excrete mercury as well as girls. That is significant because autistic boys outnumber girls by a significant margin. The theory is that boys get autism because they cannot excrete mercury as efficiently as girls

In the process of reading these reports the following question comes up again and again, and that is: Whose interest is the most conflicted? Is it the people who get paid for doing the study, or is it the people who are potentially affected by mercury, or those who are benefiting from an outcome that says mercury causes no harm?

For some reason I can't reconcile myself with the possibility that I have a conflict of interest just because I am stating my opinion against mercury. I am not making money, and I am getting nothing out of it but "Here she goes again, talking about mercury!" I also can't see that a journalist is willingly laying his career on the line to report on a problem that a "fringe" population has chosen to go on a band-wagon about. It is, in my opinion, more likely that the most highly paid entities (amalgam manufacturers, Thimerosal makers, health maintenance organizations and doctors and dentists) are also the most conflicted in their interests. They have the most to lose when mercury becomes truly known to be nearly the most toxic substance known to man.

Doctors and dentists also have an added conflict of interest, one that is unrelated to money. In case the courts make the notion that mercury is indeed what it is, i.e. really toxic (lead is recognized by the courts), doctors and dentists will suddenly find out that they have harmed their patients, and that is a shame.