That argument sounds like it would work well if he were looking to purchase a ticket, and they would deny it because they feel like denying it.

But I'm sure the ticket was already paid for, which changes the situation. EasyJet almost refused to provide the service for which has been paid. I don't know if they have a clause in their terms of service that says something like "if you say something we don't like, we reserve the right to refuse to let you board" but if it did, I wouldn't be too sure that clause is actually legal anyway.