Below are thoughtful articles on the dangers of privatizing marriage:
Jennifer Roback Morse:
Privatizing Marriage Is Impossible
Privatizing Marriage Will Expand the Role of the State
Privatizing Marriage Is Unjust to Children
The Federalist:
Polyamory Is Bad For Kids, Polyamorists, And Society
5 Questions For Libertarians Who Support Privatizing Marriage
Other Writers: Why privatizing marriage would be a disaster
Related Issues:
Science shows the stabilizing factor of traditional two-parent, binary-sex family: Supreme Court needs to read latest science on marriage: Gender and Parenthood
The importance of marriage and like topics: National Marriage Project (not a Christian organization)
Summary video: Why Marriage Matters (note the reference to “complex families” which leads to instability in childhood).