"You wanna try lifting it, I'm not stopping you." Shinjiro didn't think the guy would hurt himself, beyond maybe injuring his dignity. And he didn't really care about that kind of thing himself. He'd let Gokudera take the axe from him if he wanted, just answering with a mild, "It is kinda heavy, though."

Still. Maybe he's stronger than he looked? Ken worked hard to swing around his spear to keep up with the older members of S.E.E.S., Shinjiro knew that first hand. He's not going to tell this guy he couldn't try.

Though if Gokudera did end up looking like he might wrench his shoulder or something lifting the axe - Shinjiro would move to stop him.