I laugh at your excuses that marriage is important in reference to the prevention of a sexually transmitted disease. You obviously do not understand the nature of a disease or infection. When speaking of sexually transmitted diseases, you stated, "This is just one of many reasons why sex should not take place outside of marriage." I abhor your misleading falsification of information. Marriage does not inhibit, nor remove a sexually transmitted disease. Therefore, if a man or woman married a person with a sexually transmitted disease, they will also contract the disease if intercourse is initiated without proper precautions. Therefore it can be reasoned that marriage has no value in the prevention of contracting a sexually transmitted disease and that the previously stated "proper precautions" could be used between non-married couples with the same effect as couples who are married. Please stop misleading people.
How interesting. Let's first start with a basic fact. You did not find a statement on this web site that said: "Marriage inhibits or removes a sexually transmitted disease." Thus, you start by arguing against a false statement that you supplied. From this, you came to the false conclusion that I do not understand the nature of diseases and their transmission.
What is taught is that if people followed God's teaching where they waited until marriage for sex and each husband and wife only had sex with their spouse, then the problem of sexually transmitted diseases would rapidly decay. It would never completely go away since some diseases are transmitted in more ways than just sexually. The reasoning is simple enough for you to understand. If you never had sex before your marriage, you would not have had a chance to contract a sexually transmitted disease. If you married someone who never had sex before her marriage, she would not have had a chance to contract a sexually transmitted disease. Thus, you and your spouse's sexual relationship will remain free of these types of diseases for the rest of your marriage so long as both of you remain faithful to your marriage covenant. Not hard is it?
In your own example, you talk about a person marrying someone who already has a sexually transmitted disease. That means the partner has been having sex prior to marriage. Because the partner has violated God's law regarding sexual relations, not only is she suffering because of the consequence of her sin, she puts her husband at risk as well.
For secular articles supporting this obvious conclusion, see:
Anti-abstinence sex-ed policy fails to prevent STD explosion in California: "California has insisted on teaching contraceptive-based sex education in their schools all along. They expect teens to be sexually active. They don’t raise the health standard to abstinence… It's clear California supports sexually active teens, and STI rates will naturally explode with these policies." ... "Sexually transmitted infections soared in the British Isles when Plan B was made available without prescription in 2000. California was one of the first states to permit the sale of Plan B over-the-counter without an age limit."
Sexually Transmitted Diseases (STD's): "When someone has a sexually transmitted disease, anyone who has sex with that person stands a good chance of becoming infected. Thus, having sex with multiple partners carries a greater risk of disease than staying faithful to a spouse or long-term partner."
Sexually Transmitted Diseases: "The likelihood of contracting a sexually transmitted disease (STD) is very high today when one engages in illicit sex. This fact must be seriously considered when a partner or one preparing for marriage has engaged in sexual sin, especially in its effect on the spouse or sexual partner."
MICROBIOLOGY 101/102 INTERNET TEXT: CHAPTER XVI: SEXUALLY TRANSMITTED DISEASES "Abstinence, after some consideration, is really about protecting you and your significant other from emotional setbacks (possibly for some people) and disease. HIV could be stopped if everyone in the world accepted and practiced abstinence before marriage."