People have the right to decide who can comment on their own blog.  Think of it as somebody's house.  If they don't like you, they don't have to let you in the door.  Some people like to debate, others just want to write and voice their views.  Some people don't allow comments at all, and some people don't leave their article up for very long.  It's a personal choice.

There is nothing wrong with people blacklisting other people, or not allowing comments at all. It all depends on what they want on their blog.

JU is just a blog site.  People don't have to have a reason to delete and blacklist.  The basic standards for articles is published in the rules of the site.  Past that, each person has domain over their own blog.  They are the "admin" of their own blog and can run it as they wish.  If the article is on the forums then the admins will also moderate it, but it is up to the blog owner to decide what is written on their article and who can write it.  People don't have to allow anything on their blog that they don't want. 

People here often confuse themselves into thinking that this is the editorial page of a newspaper and not peoples blogs.