Face swapping is most certainly a good thing. For some, it remains the only and final hope of replacing an ugly mug. Let's face it, not everyone is born with a pretty face. In fact, many are downright ugly. Finally, a solution exists to help the hopelessly ugly. This is a good thing.
Face swapping may create sometimes creepy effects, but it is harmless and fun to see how different features look on other people. It can even be viewed from a critical perspective in seeing how we are all unique. How can changing facial features, but keeping everything else the same make people look so weird? It is interesting to see that maybe having a different nose or eye shape doesn't make us look better. It may make us happier with the features we do have.
Face swapping is an interesting way to putting yourself in another person's shoes, or at least seeing yourself a bit like someone else. While it seems to be mostly for entertainment, I think it could also give someone a different perspective, in addition to a laugh. We don't have a lot of opportunities to see what we would look like as a completely different person, so I don't think face swapping could hurt!
Face swapping provides, in most cases, harmless amusement. People who get bent out of shape over swapped gender in faces are falling into sexist attitudes. The only time it would be objectionable is if it were used in a bullying manner. Bullying can take many forms online, including face swaps.