Spike was a innocent little dragon. He would never just knock something out and kidnap them. However he did that to you. He got over Rarity and you were a dragon just like him. Even near his age too. He kept you in a locked room and Twilight does know about this but doesn't get involved since it would Spike's feeling and you being at the castle would be a better environment then staying with the dragons. Right now Spike just walked into the room.

Spike: "H-Hey are you still mad about the whole kidnapping thing. Listen. It was good that your here. Those dragons are bullies and mean. You should be happy like with me. If you want more time then I understand."

He's a yandere for you.