Those that believe cheap oil is, on the whole, bad, are concerned that the loss in jobs and economic activity of oil companies (and their suppliers, etc.) will be so significant that it will dwarf the increase in economic activity that comes from cheaper gasoline. Certainly, there are areas of Texas, North Dakota and other places that could vouch for at least the possibility of that happening, as they have lost huge number of jobs due to fracking and other oil production techniques no longer being economically viable with oil at prices as low as they are. Lower gas prices clearly benefit more people than they hurt. But there are a lot that are hurt and if they are hurt badly enough, their pain overwhelms our gain.
I don't think we're at that point, but plenty of wall street folks seem to disagree.