What is easy to believe is that we are not the only intelligent life in the universe. Of course, whether or not alien life forms have visited here is open to conjecture, but there are surely plenty of reasonably convincing stories, albeit no publicly known "hard" evidence.
I agree that we are not the only intelligent life in the universe, which consists of billions of galaxies which contain, on average, 100 billion stars apiece. I also believe that there are many exponential scientific advances of which we currently know nothing.
I don't know what happened at Rendelsham, and I'm quite aware of the possibility for lying, embellishing, and just plain mis-remembering after the fact by the witnesses.
I just don't see a huge airbase being sent into a tizzy by the same lighthouse they'd lived with for years ON A CLEAR NIGHT.