I think some people seem to forget this will have been through lawyers at the times, Channel 4 and with Brands lawyers. If they didn't have rock solid evidence then this would not have gone to air. Brand has been very litigious in the past and got away with other exposes and had them shut down due to the legal process.
No print media or broadcaster can just go on air and spout anything they like about someone. This will have had hours of legal time pouring over every little details. They will have checked evidence timelines, they will have seen all the texts, WhatsApp chats, photos, etc.......... I would be surprised if parts of the programme weren't pulled on the lawyers request and that's why they have been editing it right up to the print/air time.