What are the ethical ramifications of ISPs blocking selected Internet traffic?

the case in a recent controversy surrounding the cable giant Comcast. According to complaints by customers, Comcast has been blocking the use of P2P sites like BitTorrent to download movies, music, and other large files. Comcast, like most ISPs, includes a statement related to being able to use tools to "efficiently manage their networks" in their terms of service, in order to prevent those customers using a higher than normal level of bandwidth from interfering with the access of other customers. However, the Comcast issue was considered by many to be a blatant net neutrality issue—blocking access to multimedia from sources other than its own cable sources. Do you think the actions taken by Comcast were ethical? Does an ISP have a right to block selected Internet traffic? Why or why not? Was there a more ethical way Comcast could have handled the problem of some users consuming a higher than normal level of bandwidth?