Why are people surprised and outraged that farrah and Jenna are giving insults back and calling people fake, they have been put in a room and are listening to people who were nice to their face be awful now they have left.

Who's outraged?

I think it's a mixture of bemusement at them getting so het up about very little, and boredom at the same thing being said over and over again.

They weren't nice to their face.

I think they were, most of the time. We only get to see all the conflict in the house. And a lot of the snottiness we've seen them saying about them in the past, was when they all got out in the garden together, and neither Jenna nor Farrah were there.