Even though Dax didn't have any sisters, he had cousins. If he can't tolerate another man forcing them, he obviously wouldn't do it on another girl. He also didn't want somebody who would stay with him on his force.
Seeing Tia too docile, he expected her to cower and accept him but she hadn't. He just played her thinking to reveal about the night but she had left him speechless saying she will take his responsibilities.
Even though he was interested to date Tia, he had no plans to keep her in the relationship against her will.
He just wanted to know if he could really kiss Tia without remembering his first love. To his surprise, Tia had broken his wall without his knowledge.
However, after realizing he could kiss her, he wanted to step back as she was angry at him. He wanted to confirm she willingly becomes his girlfriend before anything could happen between them.
