Broken windows are inappropriate questions used to justify posting of new similar questions - "Why can't I ask X when Y exists?"
Existing inappropriate questions used to justify posting of new inappropriate questions "Why can't I ask X when Y exists?".
The term "broken windows" refers to a theory explained on Wikipedia as follows:
...theory of the norm setting and signaling effect of urban disorder and vandalism on additional crime and anti-social behavior. The theory states that monitoring and maintaining urban environments in a well-ordered condition may stop further vandalism and escalation into more serious crime.