Speaking as someone who worked closely with Eric at IMVU in those early days, his message is simple but it's not always obvious to the people who start companies.
How many times have you heard about entrepreneurs that think they have some grand vision for something that they're certain will change the world, so they go away and spend tons of VC money building something, and then it fails because no one actually wants it? It happens a LOT. Vision clouds judgment VERY often.
Eric taught me that ego gets in the way of finding out what will actually work as a viable business, and that I should question all of my assumptions (and those of the people working around me) about what's right and what's not. The metrics speak for themselves. It doesn't matter how good I think my landing page headline is -- the market will validate that through A/B testing. The trick to figuring out what will be successful is first realizing that your idea is only a hypothesis and has no merit until you validate it with customers.
Eric's and the IMVU team's willingness to let go of assumptions and try different things is the reason why IMVU today isn't a plugin that runs on top of AIM. Even though that was the original idea, it became clear really quickly that it wasn't going to work. Where many entrepreneurs would cling to an unworkable idea until the company burns through all its capital, the team decided that the idea was a failure and moved on to build something that has turned into a business that now makes more than $50mm per year.
I can totally understand the uncomfortable reaction you have, but that's kind of the point. When someone comes around and says "Hey, maybe the way that the establishment thinks things should be done is actually completely wrong," some people are excited and intrigued by the possibilities, and some have an visceral, negative response. Tim Ferriss and Dr. Atkins have both sold a ton of books exploring ideas that sound new and "out there".
I think it's unfair to classify Eric as someone who only has a reputation for "writing books and doing conferences". The "Lean Startup movement" is about keeping companies alive through the perils of infancy that usually lead to early destruction. Ask anyone who worked with Eric at IMVU and they will tell you that his passion for experimentation and validation of ideas, and his framework for building a scalable continuous deployment shop are still very much alive even after his departure. If you want to know more about the culture at IMVU, I'd be happy to comment on it.