I disagree. Or, well, maybe it's more correct to say that I see this way of thinking as fraught with danger. It's great, until you are confronted by an external, objective measure of it's effectiveness.
For example, I'm soccer dad Bob and I want to get my kid, Billy Joe, into some real self defense training. He's unruly and has a lot of energy, and he's also been having some trouble with bullies at school. Just to be very clear, I'm looking for effective self defense training for little Billy Joe.
So, I do some research and sign him up at the Starfleet Ambujitsu School down the road. They are SUPER nice, and there are lots of kids there. They talk a lot about self defense, have a lot of statistics about self defense and do a really nice job of answering all of my questions and addressing my concerns. They even have an anti-bully program that sound perfect for little Billy Joe. Billy Joe loves it because he gets to go and run around, kicking and yelling, and he's on track to be a black belt in just a few years. The school is clean and professional looking, and the cost is what I would consider to be reasonable.
All of those things above have NOTHING to do with whether the art is effective or not, but as a consumer, I would have no way to know that. All of those things would contribute to making me FEEL really good about the training. But the only way I might ever know that it's actually about as effective as day camp is if my kid gets into a fight and gets the **** beat out of him.
And truly? Even then, I would probably FEEL so good about the training that I would rationalize the event. I might say to myself, "Bob. Good thing Billy Joe is a black belt in Ambujitsu. If he didn't have that high quality self defense training, he probably would have been killed."