The U.S. military hosts the Boy Scouts at Fort A.P. Hill every year in a big, expensive National Jamboree event, which serves in part as recruitment opportunity. Costs for preparing the base for the event, use of the space, etc is all taxpayer funded. The price tag for the Pentagon was close to $10 million from 1997 through 2001, to give a cost example.
If taxpayers money are going toward stuff like this, then everyone should be allowed in.