For any subject that is sufficiently well researched, you can probably find a study that supports any conclusion. The important part is evaluating the whole body of research.
You're right about this for the most part.
First and foremost, use your down vote if you think the answer is unhelpful.
Rather than placing onerous burdens on the user in the form of more restrictive answering guidelines (no paywalls, no small studies, no animal studies, must represent every viewpoint out there), if you feel the answers are erroneous or misleading, why don't you provide another answer which is better, and let the readers decide for themselves?
Or as an alternative, you can comment on what you think is wrong under the answer and hope that the user is gracious enough to edit their answer (I have done this and been met with an impressive amount of graciousness.) The problem with this is that comment wars can ensue.
Finally (and probably the least helpful response), you can flag the moderator if you think the answer poses a threat to readers. The mod can monitor that particular user's answers for a while.
I feel that it is not only voluntary of users to answer, but an answer benefits the site. Of course we need to safeguard the quality of the answers. Place enough restrictions on them, though, and there will be many fewer answers.
This reminds me of a story heard at an Emergency Medicine conference. The push in medicine for a number of years now has been towards evidence based medicine, which sounds fine on the surface of things, but a lot of medicine is based on half a century of practice that has worked. The speaker mentioned that some things don't need to be studied to know what is useful. For example, no one has ever tested the hypothesis that parachutes save lives. He said we needed a rigorous, double blinded study for evidence. It would entail 100 people, 50 of whom were provided with parachutes in backbacks and instructions in their use, and 50 of whom were given backpacks stuffed with newspapers and the same instructions. Then toss them all out of a plane. Only then could we say with certainty that parachutes save lives because it's been studied! (And we could easily identify the placebo effect as well.) My point is, not everything will have the study you want to see. Doctors, at least, have used animal models for centuries.
Of the 105 Nobel Prizes awarded for Physiology or Medicine, 91 were directly dependent on animal research. Animal research underpinned the very first Nobel Prize to be awarded for Physiology or Medicine to Emil von Behring in 1901 for developing serum therapy against diphtheria, as it did the most recent awarded in 2014 to John O’Keefe, May-Britt Moser and Edvard Moser for studies of the inner GPS of the brain of a rat.