How to set all network adapters to private from batch or powershell?

How about this:

Get-NetConnectionProfile -InterfaceAlias "Network" | Set-NetConnectionProfile -NetworkCategory Private -Confirm:$false -PassThru

Usually (almost every time), where there's a Set-*, there's a Get-*. PowerShell cmdlets output Objects that can be chained (piped) to it's corresponding Verb-Noun cmdlet.

• Get-NetConnectionProfile in this case, returns the connection profiles that have an interface name of "Network".
• Set-ConnectionProfile. When piped to this cmdlet, you are able to grab the entirety of the object from Get-NetConnectionProfile, and modify it. I.e: setting it to Private.