Is that inaccurate? Unless the goal was to strike terror into the hearts of some insurance companies, in what way does the scale of the damages affect whether this organisation should be proscribed? Should we be proscribing Bernie Madoff next?

"chuck some paint" is a deliberate misrepresentation.

It misleadingly describes the scale, coordination, and intent. It uses a minor detail to trivialize an act explicitly intended to reduce military capacity.

Is there any scale of paint chucking that can realistically represent a terrorist threat? Is there any scale of paint chucking that should lead to proscription? Because that's the key point here. It's not "can they be prosecuted for paint chucking?" (yes, obviously), or "can their paint checking escapades have serious costs or ramifications?" (sure, lock them up!) it's a question of whether their actions constituted such a grave threat to the safety of the United Kingdom that the only way of dealing with that was to make it illegal to even support their group.

If we as a country are so at risk from paint chucking that we're resorting to proscription as our tool of defence, then we have some serious issues.