My journal and my facebook wall are galleries of my thoughts. As the artist and curator I am NOT obligated to come talk to every viewer nor to listen to every response, and I'm certainly not obligated to allow others to put things up. You do not have a right to post your thoughts on my wall or your comments on my posts, because this is my space. Out of a desire to engage, I give initial permission which can and will be revoked if you don't respect my boundaries. If I say "don't comment about XYZ on this thread" or "stop bothering me about this," or "I am not interested in debating this" respect that and stop. I am willing to give you a warning, so 99.99% of the time I'm not going to get angry unless I said stop in that thread and you didn't do it. I think I have deleted a comment ONCE. I only do that when I specifically tell people to stop and they keep on. I like for people to share their thoughts and I like for future readers to have all the context.
If I don't want to 'debate', I still get to post on the internet. I don't have to pay for my expressions by publishing yours.
Defaults and near-defaults, there are spaces that are not for you. Live with it. Do what respectful people do when told not to invade someone's space with unwanted words: express them elsewhere. People who are used to getting their way and having their words treated with deference tend to think that they are owed that deference. And privileged folk also seem to think that they should be able to use other people's space. I have never had a person who was not near the privilege pinnacle complain about me not letting them use my space for their expression.
For me, no matter what a person said, I would obey the rules they set for their page. I see it as a consent issue. My sites are my virtual being, my cyber body, and if you can't obey my rules for it, you're not fucking welcome.