When someone disagrees with you and cites credentials alone as the reason why they're right

"Oh yeah, well I've been a (insert career) for 25 years and this is how we've always done it."

"I've been a (insert career) for 25 years and I know that (something incorrect or recently proven incorrect)."

"Well, my mom is a (insert career) and she said (something incorrect)."

"(Fitness influencer) says you have to consume protein within 30 seconds of your workout or else you lose gains, look how big he is, he must be right!"

Credentials are not an argument. It's such a common fallacy to think just because someone works/worked in a field, that they somehow know everything there is to know about that field and cannot be questioned.

Even if you're an expert in the field, you should be well aware that experts are always learning, always having their views reshaped, always open to new research.

Doctors are wrong all the time, and they have to spend a lot of time learning more and keep up with the latest research. Most police officers and military service members know absolutely nothing about guns, and are actually mediocre shots at best. They only know enough to do their job.

Especially egregious when someone is fit/muscular/strong and somehow everyone seens them as some kind of all-knowing guru in the realm of health, fitness, and nutrition, which is quite dangerous. Most of those influencers got that that way despite their lack of knowledge, not because of it. Plus they had help from perfect circumstances, top tier genetics, and extracurricular pharmacology.