I am somewhat conflicted with the question of whether or not people should marry those of different religions. I have had many discussions with folks about this, but Scripture, in both the Old and the New Testament seem to prohibit it. There is an incredibly practical side to this which reminds us that when you are "unequally yoked" then what ostensibly should be the most important thing to you you do not have in common. It is hard to overcome that barrier.
That was happening in Israel. The Israelities were marrying Midianite women and things were not going well for the Israelities. It was easier to follow along with what everyone else was doing, worshiping other gods, than to try to follow what just the Israelites were doing, worshiping only one God. Moses calls the people together and as they are about to start the meeting some dude sneaks in with a Moabite woman to make things happen in his tent. Everyone saw it, and maybe they thought it was no big deal and just let it slide.
That didn't happen. The grandson of Aaron, Phineas who was a priest at this time, saw this and he could not take it. He took a spear and went into their tent and drove the spear into both of them at once. This is not something they teach you in seminary, how to kabob your enemies. But somehow he was able to do it. This sign of zeal for the Lord impressed the Lord so much that God stopped the plague that was invading the camp because of their unfaithfulness.
There is something about being filled with the zeal of the Lord which allows you to do things you didn't think you would be able to do. Now, we, of course, have to be exceptionally careful to not condone violence in the name of the zeal of the Lord. That simply is not something we can ever imply especially in this 21st century. But what else could we do in the name of the zeal of the Lord which would please God? What could you do today in the name of the zeal of the Lord which would please God, and also not harm your neighbor?