I''ll give Romney sort of a free pass on this
1. he probably was talking to a bunch of christians on the far right and actually doesn't feel the need to do this
2. did he say that it would block it for everybody or was it just something that is added to your computer that you have the right to use(or uninstall)
All that being said being in the Party that believes in the market determining how stuff works, should 3rd party porn blockers be an issue for the private markets to create? Having the Government decide to block your porn is the definition of big government.