"Only the experts' opinions should be listened because they have years of study behind them."
There are at least 3 blatant faults with this slogan.
The first one is the assumption that ALL experts actually studied years just because that's certified by their titles and credentials; but there is no guarantee that's necessarily the case: titles can be made up or bought, and even if they are gained honestly, the required level of effort varies based from the personal situation (time period, university, professors, etc.); last but not least, even years of study do not imply that someone's "expertise" consists in anything more than a blind acritical memorization of notions with little actual understanding of the subject at hand; as a proof of that, there are countless "experts" who studied years in fields like theology, astrology and other pseudoscientific beliefs, but their alleged "expertise" and "years of studies" certainly did not prevent them from recognizing the faults of their own field.
The second fault is the implicit conflation of the word "expert" with: "person with an officially recognized credentials"; this is crucial because it is arbitrarily assumed that, since owning an official degree certifies several years of study, then its absence certifies the opposite, that is: no study at all (or not enough of it), which is a glaring logical fallacy (denying the antecedent): how many years the officially recognized "experts" spent studying says absolutely nothing about how much study was done by the "non-expert"; in fact, there is nothing that prevents someone from studying exactly as much (or even more) than an officially recognized "expert" and achieving the same level of comprehension of his field of study, but still NOT get any official recognition either by choice (ex.: personal research, self-teaching) or by necessity (economic difficulties, hostility from the establishment, etc.).
The third fault is the complete misconception of how an academic scientific career actually works: since most of the time this slogan is used to dismiss opposing statements about very specific issues (WTC falls, vaccines, chemtrails, etc.), it implicitly states that the all of the experts' years of study are spent *exclusively* on that specific issue and nothing more, when anyone can easily see that's not even remotely close to how actual education works: first, about half of those "years of study" are spent on basic school education that almost anyone gets; secondly, compared to a simple personal research, the deal of time required by official education is artificially increased by the need to follow a pre-determined schedule that does not take into account the individual attitude and knowledge of the students, and to officially prove everyone's level of understanding to an authority through excercises, tests, etc.; third, an expert is never someone who knows everything about 1 single specific subject, but he must know about *all* subjects related to his fields of study: the "years of study" derive from the sum of the time spent on specific subjects which (taken individually) is clearly much smaller; no expert actually spends "years" studying the WTC falls, vaccines, or chemtrails, or other specific controversial issues; in fact, it is often the case that concerned common people with no credentials spent much more time studying such issues.