The clip below is from November of last year so it's a little dated but I searched GLP and didn't see anything posted about this.

Paul Stamets is a mycologist, author and advocate of bioremediation and medicinal fungi. In other words he is an expert in the study of mushrooms. At around the 2 minute mark, Paul refuses to answer Joe Rogan's question on what the negative effects are of eating Portabello mushrooms. Paul states that his life is in danger if he answers the question!!! Wtf! Could it be that Portabello mushrooms cause cancer and the powers that be don't want us to know?

I've done a little bit of research on this and the only thing that I have found is that Portabello mushrooms contain Agaritine which is known to cause cancer and mutations in animals. Does anyone know more about this?