Why should killing that person be any trickier than killing anybody else? As described, he can read someone’s thoughts, memories, and emotions. That is quite a different thing than him knowing everybody’s thoughts, memories, and emotions.
Plus, how could he prevent it? Dodging one assassin is one thing. Dodging 1,000 assassination attempts is just about impossible even if he knows how it’s going to happen.
He’d be the perfect moderator for presidential debates. But how do we know he’s telling the truth? You need another person with ESP to keep him honest. But then how do you know he’s being honest? Then you need another…
I agree that a single esper is going to have to keep his ability secret in order to survive. Aside from assassination risks, secrecy is also by far the best way for him to benefit from his power or to do good with it. There’s a lot of ways for the lone esper to profit, gain power, or expose wrongdoing if no one knows what he can do.
I didn’t say it was likely. If I had that power (and I don’t I swear!) I’d wouldn’t even tell my own mom. Who’s dead now, BTW, so maybe it’s safe to tell her.