Actually some airlines require a degree for you to be able to apply for a job.
Most of the airlines dont but as I said I know a few that do, so it all comes down to you and who you wish to fly for.
No one said that a degree isn't useful, we are saying that an aviation dedicated degree isn't as useful as a general management course.
If you are interested in doing management you should do a proper qualified management role that has professional status from organisations such as Chartered Management Institute, Chartered Instition of Personnel Development or the likes.
You need to use your degree as a back up, what happens if the airline industry collapses? You would be stuck.