I can see that. But we've seen tackles like that every week against our own players and thankfully it doesn't result in a major injury. Look at the Everton v Liverpool game, Mascherano was lucky he didn't suffer a leg break with Pienaar kicking him.
Ronaldo was booted up and down the pitch during his time at Old Trafford, no sympathy from rival fans. I do think players take it too far, but that Shawcross was 50/50, no malice, just an incredibly horrible outcome. Bringing up past tackles when he was younger is pointless. I can remember Gerrard flying in two footed when he was younger, Essien too. These tackles will always happen, it's part of football. It's a side nobody likes to see, and it's even worse when a player is carried off as a result of it.