Interesting topic and one ive often thought about. I used to hang out on a forum that was flooded with these arm chair experts. One guy i just started calling out on his Google Fu skills. I think it's a trait of insecurity. Why can't people just admit they don't know always.

At that one forum it got so annoying that myself and a few of the forum subject experts broke off and created a secret private aerospace forum composed of people working in that field directly. We get them first and its invite only. The conversations are so much more flowing and less frustrating. We do invite a few who are not experts on the subject but are genuine and sincere and we have no problem helping them grow their knowledge and mentoring them into scholars on the subject themselves.