It sounds to me like this person is lonely. He wants to share his interests (conspiracy theories) with someone. I'm sure he would prefer to share them with someone else who actually wants to play the conspiracy theory game with him rather than someone who has no interest in it, but maybe he also is trying to build a relationship with you by sharing his interest. These conspiracy nuts are really the same as anybody who is engrossed in a hobby. He could be into model trains and want to talk to you about model trains all the time and get annoyed that you aren't as into model trains. It's the same thing. What he really needs is to join a group with other conspiracy nuts so he has people to talk to about his hobby who actually care.