Arthur, despite the worries shared with him and that he's shared with Bruce and Tony, hasn't closed himself off to Rio'era. He possibly could, if he tried, but he's taking the plunge - figuring they'll never find out if they're traps or not if he doesn't open his mind to her to see. "She's saying you're her friend. Or that she's your friend. They communicate telepathically, apparently not just with people like me."