Parshat Ki Seitzei
In 21:11 the Torah allows us to take a captive woman from battle as a wife. This was called אשת יפת תואר.
Rashi says that had the Torah not allowed it, this man would have married her anyway, despite the prohibition - so the Torah allowed it. But you should know it is not a healthy relationship and he will end up hating her and having a rebellious child, etc.
Sometimes a person has to bite his lip and keep silent even if he knows someone is doing something wrong and dangerous, and even if you know that that person will regret it later. Sometimes people need to make their own mistakes and learn on their own.
The Torah here does not even suggest don't do it, it is a bad idea and will end badly for you. It just says you want to marry her, go ahead. The Torah is keeping silent on the pitfalls in this situation because it knows the desire is so strong, no matter what it says this man will go ahead and marry her anyway. He needs to learn on his own how bad the situation is, and maybe others will learn the lesson from seeing his mistake. But the Torah stays silent. And sometimes, so must we.