It's for the same reason why adults get mad at the 'mistress' (male or female) instead of getting mad at the partner who cheated. They have already decided to accept/forgive the 'bad adult' in the situation but still have all of their pent up anger from being wronged. So they take it out on the children, 'mistress', and/or whomever they feel is inferior instead of the person who deserves it. People suck.....
True the audacity to blame the kid, it should always been the one who do wrong should be punished and should be shame for doing it bringing disgrace to themselves.
At chap 40 sometimes I don't understand a family who doesn't like their kids or have a problem with the kid like its not their fault that they give birth to their kids like? Why hate someone you brought in this world like maybe you should put a condom if you don't want a kid and even if it was accidental or form of your affair it should been the parents fault not the kid why would you hate them for being born isn't it your fault? If i was in that situation i will always blamed the parents until they feel a sense of shame it wasn't like i ask to be born in this world? Adults are really nasty when it comes to their mistakes pinning it to the your child or kid is not really it, barking at the wrong tree tsk, I hate this kind of situation in every manhwa.