Firstly, it is incoherent. The concept of "logged on" applies to a computer, not to a network. Various operating systems implement this in various ways, and some have no such concept. The ISP has no way of knowing this information.
Secondly, the term "pornography" is notoriously difficult to define. Facebook have recently used it to prevent mothers posting pictures of themselves breastfeeding their own children. School boards in the United States who wished to promote abstinence-only education have used it to stop their students reading about safe sex. How is the term to be defined, and who will be making the decision, and how will they be accountable? Not too long ago, a Pennsylvania official who had the ability to block websites based on their content abused his power to prevent anyone in the state reading a political website which was critical of him.
Finally, the petition is couched in such terms that to dissent from it is almost to be seen to approve of child abuse. This is not a reasonable way to put forward an idea, and I wish to have nothing to do with it.
Edit: I've been pointed to http://www.crimperman.org/2012/02/29/wh