I try not to second-guess editors; they're the clients, and I have no expectation that my strip is going to make it into every paper every day.
There's always been some concern that adult subject matter should be quarantined from a page that attracts children. Unlike late at night, when 'South Park' and 'Colbert' are on, impressionable minds are wide awake when the newspaper arrives.
Having stretched the boundaries some, I'm perfectly content now to work within them. 'Doonesbury' doesn't need to become 'South Park.' You won't ever see any singing turds.