You can read studies and form opinions all you want. I do the same. But the post I replied to offered unsolicited medical advice that blatantly contradicts the currently-available information from public health authorities. ("It would be one thing if the covid vaccine actually worked well, but it doesn't. It kind of works, but not especially well. Even worse is people who actually got covid, yet they want them to get a vaccine, which is rather pointless for them.")

When you start to post bullshit online, that's when people -- very legitimately -- may choose to challenge your credentials. In fact, people should challenge your credentials in such cases. It doesn't happen anywhere near often enough, and that's a problem.

If you disagree, then you're part of the same problem. Reconsider your position.

You can’t make informed opinions on a lot of areas without the prerequisite training and context