DaasYochid: The difference between avoiding those paths where women are inappropriately clad (as described by Chazal) and installing an internet filter is the reasoning behind the move.
Making a conscious decision to avoid areas where women dress inappropriately is far MORE comparable to making a conscious decision to avoid websites of the same nature. Installing a filter is more comparable to Chazal instructing us to post guards on the roadways leading to these women; guards who bludgeon anyone who attempts to cross.
Because guards are likewise an artificial moral construct in that they exist because outside forces have decided they must, the free will of CHOOSING to avoid those paths is removed. It is highly possible that, in time, these guards themselves will be seen as the mitzvah and the purpose of the avoidance they enforce will be lost.
My intention in noting that Chazal do not demand that we avoid sitting next to women while traveling or interacting with them altogether is to point out that Chazal themselves–the ultimate authorities on human nature–believed that we are capable of self-control.
As I implied in my earlier post, I do NOT simply lock myself in a room with the computer and wage some kind of pitched battle against primal human urges. I MODERATE my own self by either avoiding the internet altogether or using it in the presence of my wife.
A filter is insulting. It implies that God created mankind lacking the ability to overcome their baser instincts without the help of a nanny. It implies that He hands us challenges that are so impossible to bear that we must simply remove ourselves from the battle altogether.