Scientific Consensus Fallacy

It is simply a lie or factually incorrect. They are misrepresenting what a scientific consensus is—how it is understood in academia (i.e., the sciences). Unfortunately, this is a concept that is not well understood by the layman, so it is easily abused. More problematic is the fact that those who disagree with science (for political or religious reasons mostly) use their remedial understanding of the concept to dismiss the scientific consensus (strawman fallacy). I think the wiki page does a good job at explaining this concept well.

Political Science, maybe?

It is simply an example of the appeal to authority fallacy.

Claiming consensus when it doesn't exist would be deliberate misinformation (lying).

If they asked, say, 300 scientists for their opinion and only 25 of them approved the medication, then using those 25 to claim your medication is "scientifically proven" would be cherry picking your own data.

Careful now. You are close to trespassing the thin line between HOW and WHY -- Best not play or place that card on already overborerden house of cards.

"hand-picked scientists."...confirmation bias, maybe

I'd call it a lie, or at least a purposeful misrepresentation by using the word consensus in a different way from how it is used in scientific discourse.  

This would be a straight-up scam. However, the general topic can involve a few interesting fallacies. I tend to believe that the whole idea of a "scientific consensus" is fallacious. I'll explain with a quote from one of my favorite thinkers:

"Science isn’t the sum of what scientists think, but ... a procedure that is highly skewed. Once you debunk something, it is now wrong ... Had science operated by majority consensus we would be still stuck in the Middle Ages." - Nassim Taleb, "The Most Intolerant Wins"

In my experience, the phrase "scientific consensus" is most often used to commit the following logical fallacies:

1. Argumentum ad verecundiam (see appeal to authority). If one authority cannot convince you to accept an argument (authorities do tend to disagree), then the person brings an entire group of authorities to bear. In your case, it's a clearly compromised group. But in most cases, it isn't so obvious. It can be hard to argue against this appeal because some critical mass of experts agreeing is generally considered to outweigh what should be obvious mitigating factors (e.g. groupthink, echo chambers). Thus, you are "shamed" (the sense of the word verecundiam) into accepting the argument despite what may be obvious logical weaknesses.

2. Consensus gentium (see appeal to common belief). Literally, I think this means something like: "agreement of the clans or relevant authorities." My understanding is it is like an ad populum but perhaps involving those with greater authority (elders, experts). If my understanding is correct, you can see where I am going with this. An entry on a Website that is the top hit for this fallacy on Google puts it nicely: "The weakness of this criterion is obvious: throughout human history the consensus beliefs of humanity (e.g., geocentrism) have turned out to be false. This principle reverses the appropriate order for determining the veracity of belief; a belief is not true because it is believed, it should be believed because it is true."

This author again hits on something critical: The word "consensus" itself suggests a matter of belief about what is true. That's not what science is about. Thus, "scientific consensus" can be considered an oxymoron. Consensus is not scientific.

One last quote to make the point:

"Years ago, someone asked John Maddox how much of what his prestigious science journal Nature printed was wrong. 'All of it,' the renowned editor quickly replied. 'That’s what science is about — new knowledge constantly arriving to correct the old.'" - Christie Aschwanden, "Failure is Moving Science Forward"