I don't see any difference compared to other industries that employ unskilled workers / rigid resources. These workers are treated everywhere as commodity and just the matter of time when they are replaced with robots.
Agencies, contractors, army, teachers, doctors, escorts are also part of the sharing economy in a more oldschool way where people don't really care about the social value of the money they pay. The difference is whether one is are part of a commodity service or not.
Some of these gripes are legitimate, but all gesture to the rest of the crowd denouncing today's symbol of "libertarian evil" to signify that all these folks, and by extension the informed in general, support their particular cause and gripe.
Lots of people think uber represents some social problem, but I would guess for most of them, "lack of socialism" isn't what they had in mind.