It's not something you come to be, it's how you start out. After that, if you do something to hurt people, for any reason other than to protect yourself, you've proven you're not safe to others. That doesn't mean you're automatically safe to others if you don't do that, because maybe you will. It just means until you actually do, there's no way to tell, unless you're yourself. For instance I know I'm safe to others because I, as myself, can authoritatively say I won't hurt anyone for any reason other than self defense. Other people are free to believe or doubt this as they see fit, but I, being myself, will always know I'm telling the truth about it.