Do UFOS exist?

Of course.

Then why don't governments admit to their existence? The answer to this is only about 25% to 40% of humanity can actually deal with this reality. The rest would have a psychotic episode and kill themselves or others like if they were suddenly confronted with a real life Grizzly bear knocking down their front door. The majority of people on earth simply cannot cope with UFOS being real.

Governments know this and so they have to deny the existence of UFOS while they at the same time have diplomatic relationships at higher levels with them.

Imagine you were about at the level of Yanomamo tribesmen who never saw a plane or knew languages existed other than theirs or knew about computers or how to make clothes the way we wear or any other number of things. What happens when they meet people who live 5000 years long or longer, have technology 1000 to 1 million years in advance of them? The same is true of most people on earth. They simply couldn't cope with the real truth. And that's the reason and they would destroy civilization because they could not cope with the real truth.

Intellectually, most people can cope with the truth but most people (a majority) would freak out later emotionally with psychotic episodes and run amuck and destroy churches, businesses, and civilization in general which would be very similar to  how ISIS is now in reaction to the truth about anything.