I'm thinking they are trying to stop targeted harassment but politicians being who they are, are probably too stupid to know how to narrow it down properly.
I can see making people responsible for trolling a specific person or spamming them with harassing e-mails (cyber-bullying). If the spamming or trolling results in something bad, the people should be held accountable for their comments. However, random acts of stupidity online should just be ignored.
Comments from some annoymous source on the internet while annoying should only be controlled by the website they are posted on. Websites create their own standards, or lack thereof, and should be allowed to moderate things according to that. If people don't like it, they are free to stop visiting that website.