Asking people to do something before allowing them into your bar is not slavery. You don't need me to tell you that saying it is diminishes the great injustice that slavery is and was.
My reading of it wasn't even that the bouncer insisted they do it. More that he or she suggested it as they were entering. This is marketing, not servitude.
It's not slavery of course, but it is a troubling approach to marketing. If I'm going to a bar on my own account (rather than to participate in some prearranged party) then I don't want to be hustled by some total stranger into supporting something I've never heard of as a condition of entry.
I know I'm out of the mainstream on this, but as a European one of the most difficult things about living in the Us is the lack of regard for personal space. Before I knew the appropriate code words I went through a stage of fending off signature-gatherers with clipboard petitions by pretending not to speak English. If you asked me to vote for something on my smartphone as a condition of entry to a bar then my first response would be to find some other place to have a drink.
Well, we can look at what was said (in the third-party retelling):
>Grace had the gutsy idea to ask the bouncer to make everyone who came into the bar have to vote for Watsi on the contest site on their smartphone
I agree that it might not be quite slavery (it would depend on exactly what happened), which is why I included tribal exclusivism, which it most certainly was (at least according to the above portrayal).
Edit: Anonymous down-voters are out, in-force, tonight!
My reading of it wasn't even that the bouncer insisted they do it. More that he or she suggested it as they were entering. This is marketing, not servitude.