The fact that the list itself is closed is not a good argument by itself not to post the link given that the link is to a public and easily accessible website. However, it probably would have made sense of it had included the request not to the post to the blog.
The post should have included an explanation of the lack of information (e.g. “the instructor posted this to a private mailing list that I subscribe to, and does not wish himself or his institution to be identified”—if this is in fact the case; otherwise, the information should have been included).
The fact that the list itself is closed is not a good argument by itself not to post the link given that the link is to a public and easily accessible website. However, it probably would have made sense of it had included the request not to the post to the blog.
The post should have included an explanation of the lack of information (e.g. “the instructor posted this to a private mailing list that I subscribe to, and does not wish himself or his institution to be identified”—if this is in fact the case; otherwise, the information should have been included).