Whats up with aliens being such a big cover up?

Well see I read about some people who found out the reason and had nervouse breakdowns, and some even suicide? Now what could possibly be that dam scary, and some of those people were military personel, so they should be trained for scary stuff. It makes me wonder if aliens were really our friends, then the secret wouldve not really been a secret, so they have to be wanting to kill us, why else for the cover ups? Couldnt they just say we have,found intelligent life on other planets and there here to help? What do you guys really think? And plz im serious no stupid or immature answers, thanks