When we create a blog post on this site, we are sharing with the community. We may be sharing our personal lives, reviewing the latest (albeit, 80+years old) shaving gear we bought, entertaining our fellow members with the history of facial hair, or arguing our political views in an essay.
When we, the members of this site, create a blog post, we are injecting our own ideas, however small, petty, or provincial, into the marketplace of ideas--however small, petty, or provincial that marketplace may be. And it does not matter how small or great the subject is, because we choose to participate here and choose to be a part of this website community.
So if one is sharing and participating in an exchange, why would one close a blog post to comments from other members? If one is sharing and laying his ideas on the table, why would he put a fence around his post?
It smacks of cowardice, particularly if the person is making a strong or controversial argument. The act of blocking comments seems to say: I may express my views, but rebuttals are verboten! And is not cowardice an unmanly trait? If one wants to make an argument, one has to be prepared to face criticism. That is what an exchange of ideas is all about.
No argument can be considered legitimate if it is closed to commentary and criticism. Without the opportunity to discuss and rebut, an argument becomes a dictated command, as if it were a decree handed down from on high. But an argument derives its legitimacy from free and reasoned discussion. And when the writer or speaker--whoever is making the argument--closes off free discussion, neither he nor his argument is any longer deserving of respect.