Well, the killer about the whole blood drinking is that, according to Ruby in Lucifer Rising, Sam didn’t even need the blood! She made him drink it just because she could. To make him believe he was dependent on her. He could have learned to kill demons without hurting the host, just with his mind. Which would still be shady, seeing as how the power comes from an evil source, but he WOULDN’T HAVE NEEDED TO DRINK BLOOD.
It does seem probable that Sam could’ve been trained to unlock his powers the way the other special kids did. But he became dependent on the drug and that blocked him from doing it another way.
But even then, there’s never really been a way to kill a demon while also sparing the host. Sam could exorcise the demon, but whenever one is killed (even by the angels), the host dies too.
Castiel says in Two Minutes to Midnight that Sam would need to drink demon blood to be able to properly contain Lucifer. (The fact that the show apparently forgot about that and how archangel vessels in general work, not withstanding). Sam still needed the demon blood, if only to contain Lucifer and Ruby, I think, knew that. It’s awfully convenient that she just so happened to bring Lucifer’s vessel jacked up on demon blood to the very place where his Cage would open.
Yes, this is an excellent point. Ruby really knew what she was doing, didn’t she? Not only did she secure Sam’s trust through temptation and deception, she also secured her dependence on her through the blood drinking, while also preparing him for his big role.The blood also functioned to make him feel powerful, allowing pride to blind him further from the path he was walking. In the end, it really benefited her to use this method, instead of the one Azazel tried with the other kids.
Ruby also had the common sense to sew discord between Sam and Dean. She didn’t have to do much either. All she had to do was present herself as this snowflake demon who could be trusted while building up Sam’s hubris and pride by convincing him that he was the only one who could save the world only to leave just long enough for him to start to unhinge and become dependent on her. Rinse, repeat. The rest would sort itself out.
imagine if Sam was stuck in that convent with Lucifer, still resenting Dean. How much you wanna bet Lucifer would use that to his advantage and coaxed a ‘yes’ from Sam?