Well, sometimes circumstances are context for the opinion. A person who's X knowns more than a person who's personally familiar with X knows more than a person who's read up on it knows more than a person who never thought of it before -- and yes, none of that is absolute, sometimes you can be entirely clueless about an issue that has everything to do with you, but generally it works.

I definitely reserve the right to think, at the end of the day, that another person is wrong, no matter what their knowledge/experience/involvement are. But if it's someone who has those things, I'll be much more suspicious of my opinion and much more careful when I make it, and much more likely to leave a window in my mind titled 'still possible that I just don't get it'.

I don't think credentials is an appropriate word here, but honestly, in some ways it's right. My opinion is not always as good as anybody's. I'm not always well enough informed. I haven't always considered things long enough to process more facts and let it sit and fine-tune my opinions. And sometimes how it actually feels to be something/live with something/etc really is a crucial factor.

Again: that doesn't mean those who have those information/experiences are always right. But yes, it's absolutely relevant information.