Because it is the only evidence that is presented, and lay-people can easily come up with objections. These people then express their frustration or confusion w

Because it is the only evidence that is presented, and lay-people can easily come up with objections. These people then express their frustration or confusion why some of these objections seem completely unaddressed. These people are effectively asking about these objections. Perhaps many of them are phrasing it differently. But, with exceptions, I think people tend not to be angry or vitriolic. At best they are frustrated. Just treat these remarks as questions. It might be annoying to get the same questions repeatedly, but that is a fault of wider communication about dark-matter.