I think he might have erased more than that.

Maybe there's another reason he wanted to forget the storm. Maybe his daughter was on one of those ships. ( It's something that's been bothering her since the memory she experienced, together with the puppet show. A nagging feeling she can't shake that Matthias is responsible for his daughter's death. It would certainly explain why he's chosen to give up so many memories relating to her. ) But you're right, no matter how much he's chosen to forget, it doesn't excuse anything.