Are these scientifically founded opinions. Not necessarily, hence why "following the science" is valid if you are following experts in their field.
If you're a software consultant, would you take on the opinions from a marketing client on the best algorithm to implement for their solution? Probably not.
If someone put in the effort and time to throughly research the topic and draw an opinion from that. Regardless of their title or their funding, then why would you discount it?