^ How many of those guys are going to run full force and tackle a person without pads though?

I was thinking about this more last night. The reason you don't see (very often) bone crushing hits in rugby is because it is impracticable. You can easily hurt yourself and the other player. Not to mention that the point of the game is to turn the ball over. This isn't football where you tackle the guy and the play is over. You put everything you got into a tackle but fail to wrap him up and just knock him over he can easily pitch it off to one of his teammates or get up and run.

As for the argument about lineman. Yeah their athletic. But how often do you see them make a huge run and not be winded. They wouldn't be able to play a full match of rugby. They need to have insane about of endurance to be able to do all of that running and hitting. And for their size, I just can't see that happening. And bigger doesn't necessarily mean better on a rugby pitch either.