Being older than someone doesn't automatically mean that the older person needs to be respected. Respect is earned. Our parents don't deserve just because they gave birth to us. They deserve our respect because they were/are good human beings who led by example and gave respect in return.
Both Ashok and Meeta disrespected Babita and Minnie. Cheating is an extremely scarring experience for the person cheated on. It affects one's self worth and confidence. While cheating is more complex than plain lust it is easier to forgive say a one night stand than a long standing relationship with another person (like Ashok did with Meeta). What they did was beyond indecent. If Ashok no longer loved his wife or didn't find her sexually attractive, all he needed to do was divorce her. There was no need to be deceitful for so many years.
Babita's reaction is very realistic, especially for a woman from a small town. Minnie too, while a brat at times, is well within her rights to chew out her sperm donor and his wife - especially since THEY keep seeking her and her mother out. The Khurrana's need to first learn to respect that everyone has the right to personal boundaries and not barge into lives that they have helped make miserable.