What makes a toxic fandom?

Personally, I belong to many a fandoms of all kinds of different media. TV shows, books, games, ect. Many of which would be considered toxic, and any internet users most likely know the ones I'm talking about.

I saw this challenge and some of the entries were deep and or political stuff, I decided to stay a little light hearted even though this could spark some push back. I don't believe fandoms themselves are toxic I believe some content creators and fans of such can be. I myself am not a very active fan in any of my fandoms but I could talk for hours about them. Some people decide the way they want to share their love for something is to bash another for having not seen or experienced it, or vis versa be so demanding about how and why its good to people who aren't into it. I've turned many of my friends off to shows before for talking nonstop about the things I like, and I know that was a mistake on my part but I'm passionate about these things. I know many people belonging to a fandom that dare to post about it are too, but sometimes it comes out wrong or their love is so overpowering that only some others in the fandom will understand and we lose potential people joining the ranks.

Passion is a powerful thing but its also terrifying in the wrong hands. (Fanart creators some of you are doing great others need to see some thearapy.) I just want to share my experience with something with others, online is usually my best bet but with so many people blaring about how their right and the other side is wrong its hard to enjoy anything.

Annnnnnnnd I'm done. Rant over thanks for listening. I know I sound like I'm biased. It's because I kinda go between too much to handle and no acknowledgement at all, and I'm trying to fix that.