There was no way the stamp was accidental, he had plenty of time to adjust his stride and avoid De Gea. This never seems to happen when a team is winning, a so called accidental stamp. This is because it is highly unlikely you'll ever accidentally stamp on someone. It was just a thuggish act of frustration from Skrtel, because his team where losing, and a 3 game ban is far to lenient. He could quite easily have done some serious damage to De Gea's leg, running and stamping on him with studs on. This sort of thuggish violence should be punished with much more than just a 3 game ban
Some of the more hysterical Dippers are insistent that Rooney's assault on Mignolet was as bad as Skrtel's stamp on De Gea. Dippers are funny when they're angry.