Are you kidding me? One of most powerful organizations in the world specialized on handling secrets and you want evidence?

They violate the US constitution and you expect them to hand out evidence?

There has been previous episodes of people (proved and documented) of people attempting to speak up and being silenced, imprisoned etc. Any person threatening to go to the press can be arrested for treason.

And if you look at similar organizations starting from 100 years ago you'll see the same patterns again and again: people who try to speak up are silenced in a way or another.