I don't know if it is possible to disable "password protected sharing" with PowerShell.
I tried:
Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\Lsa" -Name "everyoneincludesanonymous" -Value 1 Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters" -Name "restrictfullsessaccess" -Value 0
Then rebooted the machine and the "password protected sharing" remained on.