I do not see the point of this thread, at all.
It's stupid for any player to willingly take a shot that could seriously hurt them; have you seen the big hits players can take particularly on special teams?
If you are implying that taking hits would somehow equate to better yardage or greater chance of TDs.... frankly the extra risk is not worth is.
Williams is our best CB. Shields is a decent Nickel with a promising future. I really see no point in them risking getting a couple of extra yards by getting some tough contact. And, as you said, ball safety is more important that 1-2 yards we could get otherwise.
The NFL: Where Greg Jennings Happens.