I really don't think that there are do's and don't's for blogging. However, I really am getting tired of seeing the blogs that people make pointing out their views on other people then saying that they "don't mean to offend anyone". It's kind of like stabbing somebody in the eye and saying "sorry if that hurt. Don't get mad at me." It seems like people are forgetting that there is an actual person behind the post.
And, yes, your blog is your house. You have the right to say who come into that house. And, others have the right to decide that you are not welcome in their house, too.
Yeah, sorry about spilling coffee between the cushions in your couch