The poster above beat me to it with Peter Cullen's brother Larry. Larry didn't think a whole lot of his younger brother's line of work, because honestly acting and voice acting is a hard way to make a living, especially in the early 1980s. But he needed to borrow Larry's car to get to the audition, and Larry decided to give his brother some advice.
"If you're gonna be a hero, be a real hero. Don't be one of those Hollywood pretenders, don't go yelling and screaming and pretending you're a tough guy. Be strong enough to be gentle."
Here's the thing about Larry Cullen: Larry Cullen had seen things. He'd seen war and death and the atrocities that men commit upon each other. He was a U.S. Marine Captain during the Vietnam War decorated for battlefield courage (bronze star and two purple hearts). He'd lead men into battle and everything that comes with that. He knew what he was talking, and he'd learned it the hard way.
Superman is cut from the same mold as that. He's strong enough he doesn't need to be a tough guy. Yes, he can literally move mountains, but he's the kindest, gentlest man you've ever met. The thing with Superman to remember, at least from my view, is that Superman is a facade that Clark puts up. Because he's just Clark, and even without the powers... he wouldn't change a single thing in his actions.
