According to mainstream media reports, the Portland Police Bureau (PPB) thinks that Antifa and Black Lives Matter protesters are very sponge worthy. If you click on the source link above this article, right click, and select "view source" you can read the source article with a subscription. In that article you will see that the PPB has spent tens of thousands of dollars on "less than lethal" sponges to use during their daily tussles with local Antifa and Black Lives Matter activists.
According to the mainstream media, the PPB has spent $50,000 on over 3,000 sponges since July and slightly less on nearly 3,000 sponges four months earlier. It is not clear if they were just stocking up for the long haul or if they have been getting so much action that they actually ran out after just four months. The sponges have emerged as one of the PPB's favorite weapons at the nightly protests that have gone on for over 100 days, so it would not surprise us of they have used over 5,000 sponges this summer alone.
Calling them sponges might make them sound soft and harmless, but as this video shows (https://www.liveleak.com/view?t=aTuv1_1594621777) they are actually very dangerous. These sponges are shot a protesters using 40mm grenade launchers with such force that the victim seen in that video was taken to the hospital and needed surgery for a fractured skull. Most people struck by them experience severe contusions and swelling at a minium. They are considered to be "exact impact munitions" meaning that they are use for targeting specific targets. The aforementioned video featured federal officers from the U.S. Marshals or Homeland Security shooting Donavan La Bella of Portland, Oregon in the head back in July, but most of the sponges fired at protesters have been used by the PPB.
Clearly the PPB consider Antifa and Black Lives Matter protesters very sponge worthy. They would not stock up on sponges if they were not sponge worthy.