Not a statement from a Justice, but from the French man of letters and Nobel laureate, Anatole France:
( The SDMB is a marvellous thing, allowing the opportunity to make nitpicks five years on. 
)
I wonder what the rationale basis is for taxing a person differently based upon their marital status. (e.g. Single vs. Married filing separately)
Recent SSM cases have sort of eviscerated the idea that a government has some interest in regulating marriage as a means of promoting the raising of families.
No they haven’t. They eviscerated the idea that the government has a rational interest in limiting who can marry as a means of encouraging procreation and family. They say nothing at all about the government’s interest in promoting marriage via disparate tax treatment.
The definition of marriage keeps evolving over time. We no longer view the family as property which belongs to the head of household. Now we see two spouses as partners in a legal sense, and all the property they own is jointly owned between them. So it makes sense to tax the property jointly rather than individually.
If a hypothetical person named Chris makes $50K per year and another person named Pat makes $100K per year, they each get taxed at different rates. But if they get married to each other, it makes sense to tax them as if they make $75K each.