I still think that since divorce is a decision that takes a long time to make (and doesn't happen suddenly in most families), CTW should have covered the topic in a whole season-long story arc--not just in a single episode, which might explain some of the bad reactions from the test audience. (Snuffy was already a well-established character, but no one had previously mentioned any family problems that could justify a divorce. Bringing up the issue seemingly out of nowhere would've upset me, too, if I'd been a test-audience kid back in the day...)
Besides covering the divorce in just one episode, I think CTW's other mistake was choosing Mr. Snuffleupagus as the main character. His father rarely appeared to begin with (except in books); if using the two human couples seemed wrong to the producers, they could have given a minor Muppet child's family the spotlight for that season...having him visit the street and talking to an adult about problems at home, eventually leading up to the divorce itself as the season ended.