So, this art gallery that you mentioned - is that where you work? If it is, may I humbly suggest that the next time you meet up w/somebody for the first time, that you do it at a more neutral location, where they can't come looking for you at a later time?
If you have give this guy a formal heave-ho (which hopefully you won't have to do only having met him in person 1 time), I'd be careful not to mention the Scientology as being the primary reason. You know how sensitive religious wackos are.