A new softer angle towards this whole Fiasco which everyone failed to understand but, writers did try to explain this perspective and also understood this perspective. Its quite ironic, we were unable to understand this perspective and we are in love with a TV show which is all about understanding perspectives; how different perspectives can change the ideology, opinions, behaviour of an individual.
A new Perspective
The new perspective of taking this is that Viaan was very upset with Seema Dutta and, he was still upset when he knew she had dementia. He told Katha that he is upset but, can't say anything considering her condition. All he wanted to do was forgive her in such conditions . Atleast that's the best he can do for a person who will even forget her daughter. All he did was out of emotion and sympathy. (All these things aren't spoken directy but, the meaning or intention was this_
Also, Viaan came to know about the entire story, he realised that Seema was wrong but, her mother lied further to him that Seema was a gold digger mistress and took his father away from him. Now, you guys need to understand that how much impact this lie had on Viaan's life. He began to see every women with suspicion. And, this lie was the entire reason he was sad for entire life, watched everything with suspicion and all the wrong deeds with Katha.
Sumit's Parents and Foreshadowing
Many people have habit of skipping stuff and they probably missed the talk between Sumit(Aarav's friend) and Aarav. Sumit's parents got separated with consent and both were living happily and Sumit visited both mom and dad. Writers actually indirecty foreshadowed the future episodes.
What I am trying to say is that writers are not entirely wrong about forgiving Seema and Vaanya. What they missed was a little bit of development. They did forshadow it with the story of Sumit but, they had to show a bit more about the relation between Teji and Viraaj. I think Viraaj has right to divorce with Teji if he promises that his children will not suffer ,like Sumit is not suffering. We need development regarding when did Viraaj fell in love with Seema? One angle which seems fitting is that Teji was never a good person. She was overly possessive and arrogant about her status like she is right now. I think this is only fitting angle.
Yuvraaj's Angle
Yuvraaj is alive, his family is alive and he has entire future ahead of him. In his case, Katha had a choice to sort out everything but, same is not applicable in case of Viraaj-Seema-Teji Case. Seema is about to forget everything while Viraaj is dead. The entire case was 20 years old. In this case, nothing can be done to save anyone. Its best to settle the grudges of the past as it is harming more that it is doing good (This is another message from this show). Seema is wrong but, wrong happened also with Seema. She was called a mistress that too on a national television. For her wrongdoings, she got her redemption in form of Dementia. So, there is no further point in keeping the grudges and its best to move on as the past was haunting Viaan in a negative way.
So, what can you do to bury the grudges of the past so that you can get the closure and redeem yourself for defaming Seema on national television? Viaan from his point of view, who was affected the most out of this incident, in emotion, thought of clearing her name in front of media which is wrong.
Later, Viaan did admit to her mother that his ways were wrong but, what else can he do? Seema has dementia and her daughter has no fault. Viaan also said "Vaanya mein aapko Seema ki beti dikhai deti hai magar meri behen nahi?". This is indirect acknowledgement from Viaan that Seema is wrong but, her daughter has no fault.
From, this angle, everything which is happening makes sense. It is not entirely wrong but, requires slightly more development. I have faith on writers. Till now, they have masterfully handled the story with many indirect and direct foreshadowing. They will surely provide a proper explanation like they did for everything. It might take another 50 episodes but, I am sure they will explain everything.