Actually, his father tried to set him up with alpha women (with whom he could procreate), but in fact when he saw Shishi he seemed relieved at the thought that he could be an alpha, even if he's a male. But the answer is later in the chapter, because you can understand that the strong offspring thing was just an excuse! The real reason he hates omegas and didn't want his son to be with one is simply that when he was young he himself was in love with an omega woman but she cheated and broke his poor little heart... Basically he's just a resentful jerk making generalizations...
I know his real reasoning but if he wanted to keep up his reasoning he should’ve been mad right away
Well, don't think too much about it, actually the whole chapter was just surreal... I commented just yesterday that it was really crazy (like nonsensical) how quickly the father changed a mindset he's had all his life after a 2 minute conversation...
The entire manga is a bit.. what
Its so weird that the dad is opposing this because shishi‘s not an alpha. Like, if his reasoning is that he wants his son to have strong offspring then he should be against this marriage regardless of whether shishi‘s an alpha or not. If he is, then they cant procreate, ergo no offspring. If he‘s a beta, same deal. If he‘s an omega the offspring would be „weak“ in the dad‘s eyes.
Why does he bother to ask? Why does he only get mad when he finds out shishi‘s an omega? He shouldve been mad from the get go!
So weird.
(Not that I want him to be mad but its a matter of continuity)