It's not really about being wrong or right to me. It's about helping people to better understand BJJ and grappling arts. I can completely understand where you are coming from because I was once in the same situation.
BJJ is a really odd art because it's really hard to understand how effective it is against someone who doesn't know it until you actually try it with someone who's pretty good at it. I would suggest finding a legit gym and go in there and roll with a good mid level/high level blue at least and you will see that BJJ is pretty darn effective and gives you the ability to toss people around and manipulate their base to gain dominant positions, secure submission holds, and beat them to death.
I see it all the time though, people come in and say "it doesn't look that hard" until they get on the mat the first time...then the immediate response is "this shit is hard!!". Just like that body builder I've been giving lessons too. He came in the first time and had it in his mind that I couldn't do anything to him because he was so much bigger and stronger than me that he would simply outpower me. He got a rude awakening and got tapped about 20-30 times in just a few minutes. He was so impressed at how effective it was that he signed up for private lessons two times a week for about a month now.