Getting his way
Inviting the biological dad without confiding in him, asking him to walk her down the aisle, ignoring his request to invite his friends and leaving him out of the wedding announcement – that was the last straw. That’s when the guy decided that he shouldn’t accept this treatment – if they didn’t consider him as family, he shouldn’t be the one funding this wedding.
He decided to give them a piece of his mind, at the worst possible moment. As far as he was concerned, the ‘real’ dad can pay for the wedding – if he wants to be there for the happy moments, he ought to carry some of the load.