Since the drive of the common culture today is just the opposite - to mix Jews and non-Jews - it is worth reviewing what Judaism actually teaches on the subject.
[See here, here, here and here.]
Some misguided Jews like to cite King Solomon's example of relations with non-Jews as a proof-text in favor of this sort of thing.
Our Tanach recounts the stories of our ancestors and great though they were, they still made mistakes and errors in judgment. The Tanach does not shy away from including those, too. That's why, when choosing which traits of theirs we should emulate, we need to read and study carefully to understand when they did the right thing and when they didn't. We don't want to follow their bad examples out of ignorance.
Rebbe Nachman of Breslov had something to say about this...
"....during first Temple times, when peace reigned in the world, King Solomon personally traveled far and wide, and sent emissaries to foreign countries, in an effort to spread God's Word. Solomon sought to love all human beings, by virtue of their being God's creatures, hoping that this would bring about a union of hearts and enable him to have an impact on their spirituality. However, when you truly love someone and care for him, you become aware of his or her thoughts (Imrei Pinchas, Inyanim Shonim 72). Thus, gentile thoughts entered Solomon's mind. He did not realize that the thoughts of the foreign wives he had taken had poisoned his holy thinking. Furthermore, the very struggle to lift someone out of the mud will inevitably dirty your own clothes. Thus, the very desire to rouse the buried holiness in the gentiles roused the gentile desire to bury the Jewish people in unholiness (Likuty Moharan I, 59:1; Resisey Lailah 57, p. 83d)." (Chanukah with Rebbe Nachman of Breslav)
"So if you want to bring others close, you must be protected from negative influence. You must become aware of all your thoughts, learn how to assess your intentions, and become sensitive to any subtle changes that may occur within you. In short, you must judge yourself. Furthermore, not everyone can be brought close to God, and certainly not all the time. Judgement and discerning is required to know who can and when (Likutey Mohoran I, 59:5-6:Likutey Halakhot, Geirim 3:26), because even compassion for all of mankind is sometimes inappropriate (Likutey Moharan II, 7:1)." (Chanukah with Rebbe Nachman of Breslov)"At the point in time when we, as a people, are at the lowest spiritual level ever and least able to protect ourselves against gentile influence, just now is when it seems like every other Jew in the world is reaching out to make alliances with non-Jews and seeking to bring non-Jews ever closer. Who today can compare himself to King Solomon, the wisest man who ever lived and yet he erred specifically in this area.
Just know that those who are willingly working towards unity with non-Jews are not helping to bring the redemption as they suppose, but instead are actively working against it.
