What is the difference between the recent gay marriage ruling, and the 1967 interracial marriage ruling?

Both rulings concluded that state bans on gay marriage/interracial marriage were violating the 14th amendment.
The 1967 ruling was unanimous, and yet the 2015 decision was basically split, and the dissenters acted as if this decision was “unprecedented” and a “threat to democracy”.
Despite the fact that the ruling even directly referenced the interracial marriage ruling.
Why was the 2015 decision split?
Or rather, why was the 1967 decision unanimous?