Sisters are getting very manly lately...she had the gusto to do anything, and yet not do anything fisabilillah? Muslims in the West really need to figure out gender roles and make sure they work tazkiya into there.
The husband was mistaken because he has to keep in mind the emotions and feelings of his wife. Who is going to keep his side in his old age? Guys who take second wives, always return to their first wife when they are humbled by life. What if something horrific happens to him, he is paralyzed...or whatever- how is he going to get through that if he makes the woman who has devoted so much to him for so long, his enemy?
Imam Ali (radiallahu anhu) wanted to get a second wife and it was his right to do so. The Prophet salallahu alayhi wasalam told him not too, because he knew how emotionally fragile Fatima (radiallahu anha) was. That proves you need to care for her emotions and take them into account. Islamic knowledge is not dogmatic and static, it takes context into account.
The best way to prevent this is to put it in the pre-nuptial contract, so he is prohibited from taking another wife.