Actually, I'm not sure I understand why you think gay people need longer to 'consider the pitfalls' of parenting than straight ones. I believe parenting is exactly the same for straight and gay people; sexuality is completely irrelevant to parenting capacity.
Now I think it's you who are being obtuse.
If you're gay, you have to think about bringing a child into the world where their parents aren't the 'normal' family unit. One mum, one dad, in a usual family unit versus one of two mums/dads. This could be problematic for children when going to school and mixing with their peers, and something which doesn't happen in a family with two parents of different sexes.
Whilst some gay parents may not have problems, some might and I'd imagine it's something which has to be considered when deciding to become a gay parent.