This was the last Seraphapalooza question, and a controversial one to be sure. I keep writing and erasing everything I write.
First of all, it's just coffee. Just go for coffee. Have a nice chat and drink the coffee. If you discover halfway through the coffee that he absolutely detests Catholicism, insist on paying your half of the bill and smile when you say good-bye. There are a lot of Catholics out there. You do not have to date people who hate what and whom you love.
Second, you don't have to marry someone just because you had coffee with him once and dinner with him twice. In fact, you don't have to marry someone just because you had dinner with him every Friday night for two years. (It would have been kinder, however, to call it quits rather sooner than that.) Indeed, you don't have to marry someone just because you have been his mistress for the past ten years and have had three of his children although you should consider it if he's actually available.
I do not see any problem with befriending non-Catholics. In fact, we probably should befriend a lot of non-Catholics so as to not get all isolated and triumphalist. This does not mean, however, that we should put up with anti-Catholic sneers. Anyone who sneers at what you love in front of you is not a good friend.
Third, if you don't want to date non-Catholics, don't feel guilty about it. One of the biggest mistakes of my life was allowing myself to be bullied into dating a non-Catholic after I had explained that I had been taught not to date anyone I wouldn't want to marry, and I wouldn't want to marry a non-Catholic. From his reaction, you would have thought he was Dante catching Beatrice in the act of killing a kitten.
Fourth, some Catholics can marry non-Catholics and be delightfully happy, and some cannot. It is up to you to figure out what kind of Catholic you are. I myself have spent enough time with Muslim, Jewish, Anglican, Baptist, Wiccan, agnostic and atheist men to know that I would be miserable if I married a non-Catholic. In fact, I did marry a non-Catholic once, and I was miserable. My house was a mini-Belfast. His clergy were horrified when they heard how we sniped at each other in the back of their car one day. They said they hoped we didn't talk like that at home. Ah ha ha ha.
However, my old pal Boston Girl (of my book) married an American mainline Protestant, and she is very happy. She is still a devout Catholic, and her baby was baptized Catholic, and all is well.
At this point you may be terrified and wondering which kind of Catholic you are, and all I can tell you is that you have to know yourself. You have to understand which are your core values.
Fifth, when it comes to marriage, core values matter more than religion.
I am reading a very amusing memoir about the tens of thousands of Polish soldiers who made their way to Scotland during the Second World War. The Scots hastily adopted them and the Presbyterian Church of Scotland laid on tremendous suppers for them, astonished and delighted that Catholics were actually eating their food. Of course there were efforts to convert them to Presbyterianism, but the Poles couldn't speak English and didn't mind the Scots chattering on about whatever while they ate.
When the two or three Scottish Catholics around during World War 2 told the Polish soldiers that they shouldn't be taking food from Scots Protestants, they said they'd rather take food from Scots Protestants than from German Catholics, and considering what the Germans were doing to Poland, you can see their point.
The core values of Polish soldiers in Scotland in 1940 were 1) defeating the Germans 2) eating 3) chasing girls. Although Catholicism ran through their blood (and to some extent was their blood), they had exactly zero interest in the terrific resentment of the Scottish Catholic minority for 400 years of marginalization.
Although you may be a devout Catholic, it may be that your core values do not include agreement with a spouse on religious matters (which Catholic couples do not necessarily have either). It may be more important for you to marry someone of your own ethnic group, or someone of your own political party, or a vegetarian, or a fellow Marine. Social or economic class may matter more to your psyche than sectarian solidarity, and that's just who you are. It's okay.
Sixth, we don't choose our core values. They choose us. As it happens, one of my own core values is indeed agreement with my spouse on religious matters. This is because I am the eldest child of a very traditional, patriarchal family where the default position was always "Obey Dad." (Fortunately, Dad is a great guy, so the family flourishes.) Therefore it was absolute torture to be married to someone who wanted me to stop being Catholic and be something he thought more classy (i.e. Anglican) instead. I was like those robot women on "Star Trek" whom Captain Kirk tricked into attempting to solve a paradox: my head exploded. Ka-blooey. It took about seven years to put it back together. :-O
Today the Biblical verse "Wives obey your husbands" doesn't trouble me because my mother always obeyed hers, and I find it easiest just to obey my proper Catholic one although I wish he would let me have a guinea pig. So it is a good thing he is a Catholic, and I would not have married him if he weren't. "Catholic" trumps wifely obedience in my psyche ten out of ten times, and when the conversation around my table gets rather nostalgically Anglicanish I roll my eyes and make remarks.
I know that many strong-minded women (I am not strong-minded, just enthusiastic about stuff, which is not the same thing) would be horrified by my docile disposition. However, what can I do? I was basically programmed this way, and I congratulate the strong-minded on their firmness of purpose. I am sure the toughest of them could marry a ranting, raving non-Catholic (or even non-Christian) fundamentalist and just continue being themselves and doing what they want to do and saying "La la la" to his protests and generally being happy.
If you are a strong-minded Catholic woman and are completely bewildered by the whole concept of husbands being the heads of families, let alone of their wives, then certainly go ahead and date non-Catholics. When the time comes (as it almost certainly will), give them The Talk with gusto and drama.
Update: My conscience just told me to add that before the Second Vatican Council, the Church very much discouraged mixed marriages. It was believed that mixed marriages could lead to the deterioration of the Catholic spouse's faith and to the eventual apostasy of the children born to the marriage.
After the Second Vatican Council, the Church more-or-less encouraged mixed marriages as a beautiful symbol of Christian Unity or what have you. The result has sometimes been the deterioration of the Catholic spouse's faith and the eventual apostasy of the children born to the marriage. However, I know families in which the strong faith of one spouse has inspired the children to be true to their faith and the combined influence of spouse and children wafted the non-Catholic spouse into the fold. Of course, there is no faster way to make children despise religion than parents who scream at each other because of religious differences.