This has been discussed many times here and a simple search of the forums would probably provide you more information, but I think the general consensus is that you should be allowed through with your airline ID only. If they ask for a boarding pass ask to speak to a supervisor, if the supervisor still insists on a boarding pass, it's probably best to just turn around and get a boarding pass. Many people have dealt with this issue and some airports are more notorious than others. Some airports ask for a boarding pass one day and don't care the next. There isn't much guidance on why they do this since we don't have access to their SOP. My personal recommendation would get the badge number of any supervisor that tells you that you need a boarding pass and contact TSA directly about the issue.