I mean you are totally right and I agree with all that, especially the part about me being ignorant honestly, but it doesn't really change much. Whether we believe in something, right or wrong is irrelevant because the thing in question doesn't really care whether we know how it works or not.

Common misconception in play here. If a scientist enters into a commonly agreed upon topic discussion, stating "I just don't believe in x", this is just a bias and is appropriately ignored.

"I have questions about the mechanics of x which makes me think perhaps there's a y that has all the features we've observed about x" is a perfectly fine viewpoint, rooted in scientific method.

"I wonder whether the data we've observed about x is actually just noise/biased/incomplete" is perfectly valid.

"I disgree with the commonly agreed narative for no reason other than my gut" should be ignored until some reasonable evidence as to why they disagree has been presented. If we had infinite manpower and resources, sure, leave no stone unturned! But since we don't, our current scientific model REQUIRES us to ignore such claims, or else we will be distracted from actual observations.

There are, as stated in other comments, some reasons to question black holes as we understand them today, but this was presented as "my gut just says they're not real." Which is fine. They can follow their gut. It's not gonna hurt anyone. But for others to defend that gut feeling as good enough scientific IS harmful and erodes our abilities to reason about and, in the worst case, DO, actual science.

I doubt he even knows the scientific process.