It is not the ideas that are problem with landmark and Scientology is how they're using them to exploit. Being a good skeptic is also laying claim that may be Scientology and landmark are capitalizing certain needs that exist in our culture. We shouldn't just throw out the baby with the bath water just because some fringe groups decide to capitalize on certain ideas that may be controversial.
The ideas are a problem too, if they are false. It is necessary to examine the science in the movie to see if it stands up to a rigorous test of what is known. Einstein was, in time, able to successfully defend his ideas. If something is true or false, we should know that. If it is unknown, we should know that too. So examining the ideas is necessary and one part of the question. If some group is selling lies, knowing this says a lot about their motivation.
I do agree with you on the needs question, however. All these groups certainly are meeting certain needs. And if people really want to be in these groups to meet those needs, good for them. But that doesn't mean that we can't speak up and draw a distinction between the need and a less-than-healthy way to meet that need. For example, holistic health care is popular because of the disillusionment with a mechanistic, cold and impersonal view of Western medicine. Many of these accusations have merit. People are often treated impersonally. But that doesn't mean that I have to embrace a whole host of herbs from Mother Earth's bosom, let some well-meaning person do Therapeutic Touch on me, or attach myself to some device sold at an MLM party to address the needs I have to be treated as a person. The problem with the groups discussed here is they have skillfully learned which needs people are willing to pay to have met, and sell falsehood disguised as truth (exploitation) to get people in the door.
Both the ideas and the motivation have to be examined in order to separate baby and bathwater.