She didn't care whether Su HaiTan's joke was funny or not. She knew that the man in front of her was dangerous, someone who reminded her of the people back in her high school. She couldn't dismiss his attitude that had demanded for her hands to Elder Hua after watching first hand how the old woman had disrespect her.
While the old woman mocked women, what did this man do other than nodding and smiling? He didn't diffuse the situation, he didn't deny, and he remained smiling and agreeing to everything Elder Hua said. Though Elder Hua might have been an elder and it would be rude to chastise her, to know that he didn't completely disagree to how woman's position is lower than a man was enough to put her at ill ease to just stand beside him.
Not to mention he didn't respect that she had already made it clear that she didn't had a lover.
"I can explain-"