He was invited as a VIP guest and in receiving the invitation, He accepted the terms of the invitation and values shared by the festival organization. By writing an opinion piece that was against those values, the festival chose to cancel the invitation (as determined in the terms of the invitation).

So He basically lost his VIP status and access to the festival. Nothing prevented him from buying a ticket for himself afterwards, which He chose not to do (which I would probably do too if I was thrown out the premises). Still, I apprectiate Provinssirock for sticking to it’s values.