Some attendees may already have paid for their slots, booths, tables, etc. If the public also boycotts this event then a lot of those vendors attending will not make as much as they hoped from the event. If those attending can't get out of their contracts and get reimbursed then hopefully they will sue the event organizers for the resulting low attendance conditions that they created. Sad for the small mom and pop operations that rely on these shows for income, however, being fashionable for the sake of "political correctness" comes with a price.
When you're born you get a ticket to the freak show. When you're born in America , you get a front row seat. - George Carlin