The whole "not an organisation" line is just a bullshit excuse to try and excuse absolutely rampant violence and intimidation as the actions of individuals.

In the case of Portland it's actually demonstrably wrong even on the face of it even beyond the usual attempts at obfuscation. Rose City Antifa is an organised group that operates within Portland. Many other "unofficial" antifa groups have for years held social media accounts that acted in unison and worked together to organise.

They are only "not a group" in the same way any cell based organisation is "not a group". It's just when it's anything but far left thugs we usually don't accept the decentralised nature of their organisation to stop us from calling a spade a spade.