Allowing the most generous interpretation of the camp’s behaviour, this is still a clear cut case of unlawful discrimination to me. Even accepting the camp’s claim that the cause of the exclusion was the mother aggressive attitude, the question to ask is whether another parent who was also aggressive on the phone but for a different reason would also have been excluded. By the camp’s own evidence the answer is no. The camp’s exclusion was clearly related to the gender-critical subject of the disagreement or aggression. That meets the “because of” test in the EA2010.
Questions on what the child would or would not have done or said at the camp were hypothetical at the time of the exclusion and far too remote to be relevant, even allowing that the child himself has a right to be free of unlawful discrimination.
There Is clear evidence that the treatment of this mother was different from a hypothetical mother who behaved the same way but for her views on gender identity.
This is exactly analogous to the Alison Bailey vet clinic case, where AB was turned away from service after a negative interaction with staff, when it was found that another (hypothetical) customer would not have been, but for the known views of AB on gender identity issues.
Edited to correct the identity of AB!