If they were anywhere else but here, 76 might actually consider that a threat--but he's pretty sure Reaper is following the Legion's rules, for now. That doesn't mean he's going to let his guard down, but they're effectively at a stalemate. He's going to call Reaper's bluff.

"If you can kill me."

76 knows he isn't going to get any more answers, not pressing him like this. For now, he'll relent, turning to leave.