They really don't have to call a group far left or far right in their justification, because it sounds like weak credibility in search of social support. They could just call them a criminal organization seeking directly, or indirectly, to contribute to violence for political ends, which does not sound like the case here.

But if they label it far left then they get to rile their idiot supporters up.

> They could just call them a criminal organization seeking directly, or indirectly, to contribute to violence for political ends

Most jurisdictions will prosecute you under terrorism laws for that.

The "adjectives" (far-left) are there just explain to the public what kind of terrorism they are talking about.

> because it sounds like weak credibility in search of social support

And it works!