That’s not how the rule works. If a player is blocked into the returner, it’s not a penalty. If the Cowboys lost the game because of that play, it wouldn’t be looked at any differently. Naturally Cowboys fans look at it differently claiming we got screwed, because it went against us.
The applicable rule:
Item 1. Contact with Receiver. It is interference if a player of the kicking team contacts the receiver,
or causes a passive player of either team to contact the receiver, before or simultaneous to the receiver touching the ball.
I assume the word "passive" is used to describe a player who is standing around watching the ball be caught. But if that is the case then it allows a kicking team player to push a receiving team blocker into the receiver who has called for a fair catch, as was the case last night. Tolbert did not block the Chargers player into Turpin, the Chargers player blocked Tolbert into Turpin preventing Turpin from making a fair catch. So the rule, while I understand it, has a loophole created by using the word "passive". I am pretty sure the intent is to include any player being blocked into the receiver. The question for the NFL is, is this a play they want to allow?
It is a difficult play because the receiving team blockers cannot see the receiver signal a fair catch so they have to block as if he did not. But that puts them in a vulnerable position like Tolbert was in last night.