Unless I miss my guess, reality show contestants (then and now) knew the possible outcomes, knew that the network was doing it to entertain their audience and not for the benefit of the participants, and willingly agreed to sell a piece of their lives for the fame and a chance to win.
I don't much care for these type shows myself, but if there is a market for them (and there apparently is) and no one is forced to participate then I don't see any reason they shouldn't be aired.
My wife LOVES American Idol and I enjoy Trump's show. Those are actually the only two tv shows we watch in our house.