Like a few other bloggers, I've disabled the blog comments feature. In English Literature in the Sixteenth Century (Oxford: Clarendon Press, 1954), p.168, C.S. Lewis wrote: "Every man is a dictator in his own book." So too every man is a dictator in his own blog.
I posed the same question to Keith-Burgess-Jackson. He replied by comparing a weblog with a newspaper. No newspaper allows its readers to publish anything they want in it.
One blogger opined that not allowing comments is 'undemocratic.' No more 'undemocratic' than not allowing just anyone into my house. A man's blog is his castle.