What he did to music cannot be forgotten.
I am certainly not a fan of his work, but he's the result of 60 years of the music industry attempting to turn pop stardom into an easily re-creatable formula.
He's the gangrenous toe... you're angry at the diabetes.
Hits don't make you a good song writer.
It certainly does. You or I might not enjoy it, or consider it the type of songwriting that appeals to us... but in the world of "pop music" sales = good songwriter. Keep in mind, however, Max Martin isn't trying to write a deep, complex, or "important" song. He's trying to write a song that will connect with the most people, on the most superficial of levels, in order to sell records... and at that, there are few better.