As a comment on that page mentions, obscene material is not protected by the first amendment.
Three Prong Obscenity Test
Looks like it was on public property. Can a promoter make exclusions like this while on public land?
If this is a private event, no problem with how this was handled. If he had to okay for a ticket and was allowed in, should he be reimbursed in his way out?
In who's eyes? The event was on public property, so who has the final say on rules? Private property, yes no problem with what happened.