That's the reason Help wasn't needed there...

.Hi,guys.

I agree.
I know many are a little upset today that Arnav did not defend Khushi, but we have to say that I think that was the plan as it was during the Kidnapping episode. He lets Khushi defend herself until she is on the brink of losing and then he picks her up. He does the same for all females in his family, but if we notice the threshold for Khushi is high and for Anjali is low. Remember yesterday he let Anjali sit and listen to the rest of the tape.

Khushi, he did nothing when thekidnapper was saying he hit her, but the moment he trapped Khushi he broke the barrier and hit him black and blue. He held Shyam's neck twice for daring to mention Khushi's name and the only reason he did not bring back Shyam after Anjali's request was for his mistreating Khushi even after pressure from the rest of the family including Khushi. He defends her honor when needed.
In any case what would arguing and hitting Shyam today have accomplished? If you recall Khushi does not want people defending her honor over what needs to be done. When NK was going to call the police because Shyam was manhandling her,she said Arnav's life was more imp.
In the revelation episodes when ASR asked her repeatedly why did you not complain to me even once about Shyam's mishandling when you are accusing him being of such a bad person, and her answer was because of Di. In any case good that CVs show that ASR and NK did not loose focus, which was have Di learn what Shyam is without interference about having to save Khushi's honor, which was a joke considering Khushi's honor here was not in stake at all as every person excluding Di knew who was at fault.