Unfortunately there's a lot of misinformation out there about different weight-loss programs. I completely understand your needing to rant over this!
I do, however, think that sometimes it's the weight-loss programs themselves inviting their own criticism. Some can be quite secretive, obviously wanting people to buy the book, sign up to the program or attend the meetings before they can find out exactly how the program works. It's no wonder many people get confused as to how they work if they don't have free and easy access to the information! And sometimes it's the weight-loss programs themselves that spread misinformation about rival programs, wanting their members to believe that they are the only one with the answers.
Some people sadly become diet zealots, spreading misinformation about other programs because they so desperately believe their own methods are The Way for everyone.
Another thing is that programs change with time. Some of the criticisms I've heard directed at Weight Watchers are based on their practices of thirty years ago. So while the detractors in that case are technically correct in their criticism, it's usually about issues that WW have already addressed and fixed.
When it comes to WW I for one found it worked quite well for me and it is based on sound principles, but even though it is cheap compared to many other programs it still wasn't cheap enough for my student budget.
On the bright side, at least it's getting the questions out in the open. If critics keep their mouths shut and never get their views challenged then they're never going to learn more about how different weight-loss programs work. While defending Weight Watchers must get tiring, you've done a great job in informing people about it!