Generally an opinion should be informed. Whether that information comes from first-hand experience or some other education is less important. But, again, there should be some actual knowledge rather than, “Gee, I just thought of this idea and need to share it.”
I do not comment on bodybuilding competitions. I know how to gain muscle and lose fat, but I do not have any opinion on water manipulation, or drug use (beyond some recommendations that would apply generally).
If someone said, “I need to cut 5 pounds for a bodybuilding show, what should I do?” do you know what my answer would be? Nothing. I would not comment because I have no specialized education or personal experience. I would STFU.
Now, if someone wanted to cut weight for MMA, I would have an opinion.
So, yeah, people should know what they fuck they are talking about before they start talking about something.
When guys talk about MMA fighters using steroids to “get jacked,” I know that person is full out shit and completely outside of the scene. It’s as revealing as saying a mixed martial artist should have a 3X BW deadlift, lol. Some things just tip people who know off that the speaker is full of shit.
There is nothing wrong with ignorance. There is, however, something wrong with sharing one’s ignorant views.