>Do you think it was progress when they repealed their Prohibition of Mixed Marriages Act?
Yes.
> Or did it help lead to gay marriage?
Although I agree with one and not with the other, I think they are somehow related: people don't simply accept what they have been told for generations is the right thing to do; rather, all institutions, customs, etc. are being questioned. In a way, this is a good thing. Let's just hope that whatever remains, eventually, will assist the well-being of all.
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)