My opinion: it's the padding on the other parts of the body (particularly the shoulders) that makes NFL so dangerous. If you ran directly into someone at full s

My opinion: it's the padding on the other parts of the body (particularly the shoulders) that makes NFL so dangerous. If you ran directly into someone at full speed without padding you'd injure yourself as much as you'd injure them, whereas the pads NFL players wear allow them to use their bodies as guided missiles. Rugby collisions (generally) happen at lower speeds, where the intention is to wrap up and grapple the opponent to the ground, not blast them off their feet. (There are also on-side rules in rugby, and no blocking away from the ball, so many, many fewer blind-side hits occur.)