It would have defaming if Om in front of his family asked Gauri to go for a test, it would have been disrespecting if he in front of his family asked Gauri who is the father of the kid as he thinks she is characterless, it would have been defaming if Om would have told his family she acted as a mistress of Kali Thakur.
How much he hates her, how many times he was made a fool out of himself in front his family he still keeps his relationship with Gauri as a private affair still talks to her in personal in privacy.
I should seriously learn the meaning of defaming/disrespecting words