Nice guys don't feel inadequate. Jerks do. Want to appear as inadequate as you're feeling? Act like a jerk. Most jerks (online and in real life) have done nothing of value going on in their own lives. They're cowards who hide behind fake confidence. All they can do is find fault in others because they have no direction or courage to do hard things.
It's always easier to tear others down than it is to build yourself up. It's easier to demand respect than to earn it. Of course, the easy way isn't always the best way.
Years ago I made a trip to a powerlifting meet where I was going to help some great lifters and world record holders. During one of the breaks I had lunch with a small group of people, one of whom just didn't fit in. He had an opinion on everything, but nothing to show for it in the way he looked, his lifts, or who he coached.
Later, I discovered he couldn't cut it in three well-known powerlifting groups in his area. He got no respect from all the local lifters because of his big mouth, his inconsistency, and his inability to train hard and be helpful. About a year later, I saw the same guy mouthing off about everyone on a powerlifting forum with an "I'm the man" attitude. I have no idea what happened to this guy, but I bet he's the same crappy lifter he always was.