I think the difference is that Anna and Josh have opened themselves up to the public and as such, invite questions. Banning someone because they asked a question, if it was in a relatively respectful and civil way, just causes more problems. They get enough comments that if they don't want to answer ... just don't answer. They're not obligated to respond.
Of course, there a difference between "wow, how did you manage to afford a family trip for 7 people on a one salary household, that's crazy" and "you moochers can't even get a real job, did you fund the trip by begging?". You ban the latter, but for the tone, not the question. You don't want to answer the former, fine, don't answer, but banning just looks like you're to trying to clean house and hide.