Maybe i'm bias, Shelvey comes in one footed and with his studs down and SIDE FOOTS the ball, the reason he got sent off was because he lunged a little. Steven Gerrard does this ALL the time though and it's fine because it's Gerrard, i'm willing to bet the reason Shelvey went is because he's given himself a bit of a reputation of tackling dangerously. As for Evans, well he jumps in two footed with his studs showing with all his weight behind the tackle. The correct outcome of this tackle was a yellow card to Shelvey and a red to Evans, however considering the occasion, an occasion where you want to see these kind of tackles, a yellow each way would have been fine.
However this is by the by, I've always been a bit of a Shelvey skeptic, however he told Ferguson how it is, he's my new favourite player.
The ref have a fantastic view to Evans coming in with straight legs... It is fantastic that he let him play on.