A big challenge for modern biomedical science (and for others, like climate change, for example) is that the evidence is often that effects may be real but they are slow, slight, or statistical. What is barely observable year by year can turn into an ice age--or an epidemic after much time or many exposures have occurred.
False ideas under such circumstances can be very costly. That's why what now appears to have been outright fraud in associating autism with somehow-toxic childhood vaccines has been so serious. Countless parents shunned vaccine protection because they believed the vaccines were dangerous. Huge amounts have been spent on the diseases that would have been prevented, on morbidity and serious ill effects, and of research dollars and resources.
The problem became public and political, with parents advocacy groups, lawyers, and politicians getting into the act. Other problems might have been addressed with the same funds.
The physician who has been accused, Andrew Wakefield, naturally denies the allegations. Accusations fly back and forth, and those who believe (or hope) in the conspiracy theory that the attack on him is from Big Pharma trying to protect their profits or from lawsuits, include advocacy groups that have been attacking the vaccines for some time. Every side, as usual, sticks to its story. We're not in a position to judge, of course, but there's a deeper point.
There is no easy answer for these situations in which causation is statistical and causal effects small. We have to work out various criteria for making inference about what causes the ill outcome, or what its mechanism or cause-effect pattern is. We have to work out societal risk-benefit assessments. So it is very serious indeed when we can't trust the good faith of the evidence as well as its epistemological shakiness.
No matter how much we criticize science today, and no matter how much hyperbole, dissembling, shading and stretching of truths goes on, it is assumed to stay within the lines at least of technical accuracy. So when there is fraud as has been claimed in this case, or data cover-ups as has been repeatedly claimed for drug trials, the crime is a crime against society and is very serious.
Fortunately real fraud of the data-faking kind seems to be very rare. When it happens, sanctions have to be strong, to make as sure as we can that it stays very rare. In situations where the truth is easy to find, fakery has little chance of getting the faker anywhere. But in the common situation of complex causation, cheating can pay off. So we have to be rigorous in preventing it. Generally, we seem to be doing well, and part of the evidence is the degree of publicity that the occasions of real dishonest science receive.