The people that spread this shit probably just quietly moved on instead of posting a correction and apology. The people that read their shit then never saw the truth.

A lie can make it halfway across the world before the truth has had time to lace up its shoes, to paraphrase an old adage

There could be a complete genetic breakdown of Khelif posted tomorrow to every news outlet that proves, conclusively, she is a cis woman, and it wouldn't matter. The lie that started everything is more interesting and has more staying power

People who aren't invested in it but who hear it casually in "reputable news sources" aren't going to inform themselves on any corrections, the damage is already done

I carry an old timey leather doctor's bag full of rusty pliers and laudanum bottles so if I ever get into a debate I can lift the bag and say "as a doctor-" before spouting off.

If you're actually informed, couching your opinion like this dulls its impact for no good reason. It's good to speak/write confidently when you have cause to be confident.

Hedging is great for situations where you aren't confident, but should otherwise be used sparingly.

people who have literally never been quiet?

Oh I assure you the people who you want to shut down "did their own research" and were even encouraged to do so

the opinion on the topic you are not informed about displays your values and having it might be beneficial to you.

And it might be detrimental to you just as easily. There's no way to know which without being informed, but an ignorant opinion based on "values" (aka vibes and what you want to be true rather than what is true) is more likely to hurt you or others in the long run. Just as being a racist bigot who has a wrong opinion about people of color might find that holding their racist opinion is immediately beneficial to themselves if they're in a similarly bigoted community, being a bigot is ultimately harmful for reasons I would hope wouldn't need to be explained.

An example would be a parent who doesn't want any gender-related issue to be discussed in the school.

Yet their uninformed opinion is harmful. Gender issues are inevitably part of our world and learning about them will not only prepare children to have an understanding of them that their ignorant parent lacks and help make the world safer and more livable for everyone as a result, but if that child themselves turns out to be gender stereotype non-conforming, then learning about those issues will help them better understand themselves and potentially save them from much of the misery inflicted on them by an ignorant populous.

An example would be a parent who doesn't want any gender-related issue to be discussed in the school.

Are they inherently flawed and inherently hateful individuals?

Yes, for the reason Dirt_Possum stayed below. They have a responsibility to properly educate themselves on issues that effect their children or decisions they may make that impact other people's children.

Not wanting to explore issues like gender or race is part of why certain forms of bigotry have proven so persistent.