Look, let me clear the air:
A foul in its bear definition is expressed in its entirety, from the intention of a player, the actual execution of a tackle and follow through thereafter.
Yes, Pepe did not intent to be malicious. Yes, the execution of the tackle leaves a lot to be desired. It was a "danger-threat" type tackle and the manner in which it was made was unforgiving,( could he maybe have turned his back for a ball-block.? =possibly, could he have allowed Alves to swing out his boot in thinking that ball had no potential far-travel.? = possibly, could he have made an earlier contact to win ball and have Alves fouling him instead.? = most possibly ) these are all defensive options which Pepe could have employed, given the circumstances.
Collina would have Red Carded that given the exact circumstance, Webb would have Red Carded that given the exact circumstances.
Simply, The execution evidence showed high boot, visible studs and an incoming leg with little option for diverting in time enough.
Pepe walked the plank and Fairly so imo.