It wasn't just a channel, their bond. It wasn't just them revealing their feelings to one another. It was their feelings pouring into one another, blending at the edge, bleeding over into what the other one was feeling. And that's how Leon's insecurity fed right into Andrei's, the two forces meeting at the crux.
Andrei wasn't good at loving others. He hadn't had much practise. He especially hadn't been good at being loved by others -- he'd only managed that once. Unconditionally. And he'd fucked that up. Leon was picking up the distrust, but it wasn't distrust aimed at Leon. All that distrust was aimed at Andrei himself.
Not that Andrei knew. When people confronted him, he only had one response. With a rough shove, Andrei tried to shake Leon off, into the freshly cut lumber. "Fuck off!"