Did he have all the information? Did she think it through? Does his conclusion make sense?
It’s not about the person, it’s about the information the person is providing. Is the information accurate or not?
Experts sometimes step outside their circle of competence to comment on things they’re not well informed about. They may sound just as confident and articulate as they do when speaking about their own specialty, but this means nothing. Only the information matters, not the way one speaks, or one’s credentials in other areas of study.