It is easy in the tech world (and HN is mostly tech) to confidently say 6 months is a long time for unemployment. At the moment, I'm fairly certain I could have interviews in a single digit number of hours, but that isn't true for people who have to compete for "general skills" jobs (i.e. those that require a resume, but no particular special skills, such as receptionists, admin and the like). Also there are a lot of perfectly valid reasons to have a 6 mo gap (the biggest is maternity leave).

Resume blasts are often the only realistic option some people have for getting their candidacy out there. If they had a friend at a firm that was hiring they'd probably have used that before 6 months of unemployment. Unemployment generally means that hanging out with employed friends has to be cut back (because going out for drinks gets expensive). If you network fails you for a few months you might not have much of a network to lean on after that.

Discrimination against 6 Months+ of unemployment certainly has some objective basis. Discrimination isn't always a bad thing. Still there are undoubtedly people swept up into this bias who should not be.