His stepfather lost the person he loved, or actually a bunch of them. Shirou isn't losing Rin. I'm not sure he's planning to return as a hired killer to look after his wife and children. He might choose a more moderate way of doing things. Archer never had such bonds. Rin also promised Archer she will look after him, so if he's about to make a mistake, she'll help him stay on a better path.
You have no faith in love, KrayZ33! No romantic bone in your body.