The interesting thing about this is that there is now evidence (see: Navy videos), and we have also seen what the US government does to people who try to show classified documents as evidence (see: Snowden, Manning, Assange, etc)
Snowden et al looks like counter evidence to me. People who release evidence of secret programs involving UFOs end up doing book tours. People who release evidence of secret spying programs end up in exile.
If there was evidence, there’d be evidence.