I've been eating raw mushrooms for decades and haven't died yet...
There are some which do need cooking though, but most supermarket mushrooms can safely be eaten raw. Certainly buttons, shiitake and oysters. I haven't done one for a while, but a mixed raw mushroom salad may well turn up on the Dinner! topic soon.
Obviously, wild, foraged mushrooms need to be positively identified and whether they need cooking ascertained. Many do; some don't.