Menka took vows to be with him and was supposed to be his support, but Yuvraj was supposed to bring glory to the Garodia name. I think there is a big difference between forgiving children and a spouse. Children make mistakes, but it is the job of the parents to put them on the right path. Menka always knew Yuvraj was not good, but hid all his faults, but had Suryakant known he would have taught him a lesson rather than over look Yuvraj's mistake. I think in some way Suryakant blames Menka for everything because she had the knowledge of how her son was, and didn't help to change instead encouraged him with his deeds. Yuvraj is someone who was always pampered and never saw life other than that, so he is bound to make dumb mistakes. But his mother knew of his intentions and even encouraged him in some rather than teaching him right from wrong.
I think Suryakant was right in not forgiving Menka, and I also think he forgave Yuvraj way too easily as well, because Yuvraj has not even tried to repent for his mistakes yet and proves how much he loves his family.
This is just my opinion though, hope no one is offended.
-Pawan