I don't think he'd be an easy once to convince, Steve. He's got the time travelling stone, he must have used it before. Maybe if he saw for himself, he'd be more receptive. But you're not a match for him if it comes down to it, sorry Steve.
Just ask her to destroy the stones? She knows there was a matching one in Vision's head, and she's not stupid. Wanda's the most powerful of all of us, but she uses it too well to blindly follow you.