Nah, I wasn't implying that Jack was acting OOC or stupidly here, just that his plan has a rather fatal flaw.
Still, Rider has no real reason to fight him. She won't be too pleased about the whole "trying to eat Sakura" thing (true or not, she'll trust Taiga and Kiyoshi over him), but the distance in relationship from her own master is enough that she won't go mad over it.