I don't know why, I've never had a problem tossing a bunch of shrooms dried or fresh in my mouth and chewing them up. I actually like the taste. It's the consistency that I don't like.
when they are well dried they kind of crunch up then get chewy after they soak up your saliva. I've done it where I just pop them in my mouth and chew really fast so they crunch of into really small pieces fast so I don't have to deal with the rubberiness that they get to when rehydrated in your mouth.
The way I like them best is mushroom tea (if they're dried, which they usually are). Lightly re-hydrated in warm not hot water for a bit, I drink the tea, and then chew the mushrooms up after re-hydration.
At one time in my life, I was able to get quarter pounds fresh like they were just picked and those aren't at all nasty, just taste a little strong but not at all unpleasant and the crispness of the mushroom flesh makes them easy to chew up and swallow. That is the best way I think. Fresh.
I remember picking up a QP and waiting for my brother and a friend who didn't show up until way, way late. I had started eating them when I figured they'd be here soon and they still didn't show up for hours so I just kept eating them. When they finally got there, there was only an eighth ounce left. So I ate almost the whole thing. One of my most memorable trips.