Br. Sufi_Taliban, it may be better to leave off all the details you have mentioned about the bookstore, as that was your own personal experience, and it doesn't really affect the buying of every buyer as not everyone is going to face the situation you face; buyers would just go in, pick their books, and come out, and not go through the tiring discussions that you went through. Moreover, it's not like the brother is out there to 'get every buyer' and 'convert them' to a different manhaj. So it may be better that you do not disclose your personal experience in public like this; especially the name calling can be considered as back biting, and you may be held accountable for this on the day of judgment; also, it is also possible that the brother has repented from any errors. Jazaakumullaahu khairan.