You see, that's the problem. You don't know who they are. I don't know who they are. It's the human condition: you cannot see the soul of someone else. You will never have faith in a person: only in what the shadow you see.
Someone who seems nice and genuine is not necessarily a good person. Certainly not when they start to attack and manipulate you. You thought you could trust them, but then they show that you misread them entirely and the trust will be used against you. Then you can't tell anyone, because they all see the cover image of a nice person. Since our society can't deal with these nutzoids until they go postal and commit a crime, I'd rather be on the defense. The last thing I need is to deal with another kook who can damage my reputation.
As unfeasible as it may sound, you can see the soul of someone else. Getting to read a person's soul isn't something easily achievable, however, which makes us think it's impossible within human boundaries. For that to become even remotely possible, you have to know who you are. Without that, anything further will sound just like pure imagination.
Indeed, human beings aren't one-dimensional as one would like to think. You cannot avoid being hurt when you open up yourself. Though, it's the very same action that will lead to others showing their true sides more and more. There is nothing wrong with believing in people. That said, there is something wrong with believing in them more than you trust yourself.
If you are really hurt by the fact that people are covering themselves with images and not being completely sincere, I'd suggest you to stop worrying about your reputation. It's nothing but a cover image people hold of about your personality, after all.