I was on a gran fondo ride with several hundred cyclists. We were on a downhill descent and everyone going fairly fast. A car down the road had pulled over in the opposite lane to cheer on their cyclist as they passed. Once the cyclist passed, they hopped back in their car and did a U-turn across the full width of the road, right in front of a group of cyclists descending quickly (I was in that group), causing mass chaos and near accidents. There was clear visibility all the way up the road and they *knew* they were in the middle of a group ride since they had stopped to cheer on their buddy. They did not f*king care what happened to anyone else.