How can a person dispute the prevailing scientific opinion if he doesn't understand the scientific basics?

There's nothing wrong with ignorance of a subject (we all are ignorant of some fields of study), unless the person acts like they have knowledge or understanding that they don't. A little humility by people, when it comes to discussing things well beyond their own academic or professional experience, would be a nice thing. But civil discourse and intellectual honesty takes more effort than some are willing to put forth.