While you have a point tsunade explicitly tells him he doesn't need to marry if he doesn't want to( which would equate to putin telling he does not have to marry since it is not necessary in your example). Though it is understandable that he accepts because 1) he is under danzo's brainwashing(since it was explained by the system that to counteract this he either needed to choose kotoamatsukami as mangekyou ability or upgrade his sharingan to the eternal mangekyou sharingan and since he has not done any of that yet danzo still controls him) and 2) his goal seems to be the protection of Konoha so him accepting a marriage that assures an alliance with one of the other 5 great nations is probable(though I do admit that him going through with danzo's order to kill temari after their first child is born even without danzo's control would be credible since baki, temari's sense, killed the person he had the most attachment to{ with only his parents potentially being more important to him} so he should have hatred for suna and especially for baki which is something totally normal for residents of the Naruto world as mentioned and displayed several times throughout the story)