Of course he didn't try to discourage them. He wanted to do this type of research/experimentation, which is almost certainly why he was known to the communities the parents were a part of (the article says the parents learned of him in a "WeChat group in which parents of children with autism and similar disorders trade advice").

This is a form of doctor shopping. If you really want something, you can find someone who is willing to provide it, even in fields like medicine where practitioners are expected to adhere to rigorous ethical standards.