"I'll give you Mr Scrooge, the Founder of the Feast!"
By including this toast to Scrooge despite the terrible way he treats Bob - Dickens exemplifies Bob's patience and compassion, as he is grateful and good-natured towards his employer regardless of the way he is treated
Bob refers to Scrooge with a title ("the Founder of the Feast") elevating his position and attributing importance to him - even though he does not necessarily deserve it.
alternatively - Dickens does this to once again highlight the superiority of the rich over the lower-class, as even in his apparent absence Bob gives Scrooge a sense of respect and honour.
presents Bob C as generous