You make a good point that people can only talk about the same subject so many times before it is tiresome. Another factor, I've experienced and have heard from others who feel the same, is that it isn't always accepted to express opposing views. It is discouraging for posters to be shut down in amicable conversation. I've seen it go the other way too, where trolls, who have stated intentions to cause harm, are tolerated, even the loss of well meaning posters. It is a tough balance. I don't envy the job of the admin.