1) their young family members need to take care of them. increasing oas is in the benefit of young people for that reason - it means that granny is not their problem. if granny can't afford to live on her own, she becomes your problem, and that is the thing young people want the least.
young people want the government to take care of the elderly. they don't want to take care of their family members, themselves. this is progress in a socialist society, as taking care of your aging parents and grandparents is a costly waste of time.
2) a lot of them won't get support from their descendants at all and will end up on the street or in hospitals.
3) the result is that the healthcare system gets overburdened by old people, and the social safety net gets overrun by them, as they end up in shelters and taking away resources from the disabled. this is not a scary possibility; it's actually already true.
the logic employed by the liberals is something you'd expect from a far-right government run by somebody like mike harris. the liberals should reverse their position immediately and issue a public apology for being short-sighted and stupid.
if they can't afford to take care of people, it's because taxes are too low. they should raise income taxes on the wealthy to cover the costs.