Throughout most of the Old Testament, those groups commonly referred to as Gentiles were thought of as lower.  Even in the Gospels, the Savior didn't associate with many who weren't of the House of Israel, but, when the time was right, He sent His Apostles into the Gentile world, causing a great upswing in believers.

In the same vein, because we try to follow His example, does that make it wrong for us to associate with those who might not want to do so?

As I understand the question asked in this thread, it's a question of whether or not it's okay to mingle with others in a place where it's well publicized if bad things happen:  Drunkeness; loss of virtue; gyrating dance moves; even some that result in the death of innocent babies.

However, these, and I make this statement full well knowing that I do, are the rarities.  With the hundreds of bad stories coming from Prom, there are thousands, if not millions, of stories of kids who go and have a fantastic time.

This would be a case for straining at gnats, where the vast majority remain unsullied by the bad although a few, here and there, slip up.

So, in answer to the question…no, it's not unBiblical, not at all.