Yes, Clare, but many people could (and do) say the same thing about TV, going to the mall, etc.
Also, you'll note that "it's not a sin" doesn't carry a whole lot of weight here. CathInfo is NOT Fisheaters.
We're more interested in God's design for things, the way things should be, etc.
And all the things I mentioned (TV, the mall, and mixing races) is usually not in your own best interest.
God meant marriage to bring families together -- and while it's true the Catholic Faith trumps everything, and can be a great bridge, it's also true that you want to find someone SOMEWHAT LIKE yourself and what you're used to.
Plenty of failed/split/troubled marriages can attest to this. You can't just take two people and make a marriage just because they "hit it off" at one time or another.
In theory, two cholerics could stay married 50 years until death. But usually a choleric seeks out someone more passive, and those marriages work out much better. Same goes for poor vs. rich and many other categories.
That's why classic wisdom advises things like, "What does his mom think of her?" "Does she get along with his family?" etc. More often than not, they are good indicators of how the marriage will go.
God has his ways, the Devil has his, and when you stick to God's plan and ways of doing things, everything goes along more smoothly.
I attended a very mixed-race public high school. And I'll tell you what -- everyone, for the most part, stuck with "their own kind" even though there were no forced segregation rules. You should have seen the lunch room! It looked like 1920's America.