I think I gave an explanation in post #2.
Why have people happily drifted from Aikido to other arts, or even cross-trained in other arts alongside Aikido, for decades, and not felt the need to go on the internet and claim they have found "the true Aikido" and that the various Toms, Dicks and Harrys have to admit that the entire art is flawed?
Skeptics of those who go through the born again process or of Aiki as a subset of IS are free to disagree.
If you see the (martial) arts world in a fundamentally different way, you may want to show it with others, even if you don't have a full understanding.
Note: I am not a born again christian.
I find the monetary angle kind of comical. Most people aren't going to fly out to someone else's dojo and teach a dojo for free. They would need to at least cover their costs. That being said, most of the IS people I have met will freely show what they know outside of seminars (if they're in the area), or invite people to check them out at their home dojos.