This is a good move on Senator X's part. This may eventually go about several evolutions until the right approach is found that will be accepted by the Senate at large. I think that the issues of specific wrongful treatment of members should be the reason for the inquiry. Once specific laws can be put in place concerning the wrongful actions by 'religions' upon their members, it would then become illegal to do so. After which if Scn continues to commit such wrongs.. (as they are likely to do so), then members could have them arrested, tried and convicted for their actions.
This is how France very effectively prosecuted them for fraud and forced them to pay fines as well as put up signs at the entry warning public of the potential harm.
Going after them as a religion, once that is established, would be a long and tiring process that only stands a 50/50 chance of success at best.