Because of the invite and reputation system. If someone from /pol/ wanted to come in just to fuck with things, the first barrier to entry would be getting an invite (admittedly not that hard) and the second thing would be if reputation drops too low too quickly there can be some nasty consequences (temporary bans becoming full bans etc etc).
If there were an anonymous posting system, someone with even a basic modicum of patience could come in, work on the rep for the profile until it was good enough and then hand the login over. Since there would be no way to trace the harassing/trolling/spamming content to its source it would just run rampant until an actual admin intervention.
Because of the invite and reputation system. If someone from /pol/ wanted to come in just to fuck with things, the first barrier to entry would be getting an invite (admittedly not that hard) and the second thing would be if reputation drops too low too quickly there can be some nasty consequences (temporary bans becoming full bans etc etc).
If there were an anonymous posting system, someone with even a basic modicum of patience could come in, work on the rep for the profile until it was good enough and then hand the login over. Since there would be no way to trace the harassing/trolling/spamming content to its source it would just run rampant until an actual admin intervention.