I find that on the internet there's two reasons why Catholics despise a certain bishop.
1. There is a public sin. Either they were directly the offender or that they are involved in someone else's sin such as the aforementioned covering up of sex abuse cases (which is a sin by itself).
2. They've been branded as "modernist Liturgical innovators," those who like bare churches and Protestant themed music, those who like EMHCs and girl altar servers, and those who deny requests to have a Latin Mass.
We know Cardinal Mahoney is #1, not sure if he's also #2.