Ordinary people doing not so ordinary things. That quickly sums up, what reality TV is about. It is actor-free and unscripted.
Reality TV is usually highly edited, so the genre is not unfiltered. It has become popular amongst viewers to watch, and for producers to make, because of the cheap production.1
The opposition of reality TV will argue that the content is entirely inappropriate to the main audience, which, in their opinion, is teenagers and children.
The language is harsh, the people are dressed slutty and the content is offensive.2 Especially teenagers are easy to influence, and these shows can give them expectations on how to look, act and dress.
Others will emphasize the fact that reality TV is made for entertainment, and is watched for just that. Therefore, the viewers are (or should be) capable of distinguishing reality from entertainment, when watching reality shows.
In my opinion, reality TV can be a great source of entertainment; it usually avoids discussing heavy topics and stick to fun and light entertainment.