Is it forbidden for a husband not to greet his wife's sister's fiancé, under the pretext that he does not wish to establish a relationship with him?

Extending greetings (salam) is among the apparent rituals of Islam and a cause for love among Muslims. It is a Sunnah, and responding to it is obligatory, based on the Almighty's saying: "And when you are greeted with a greeting, greet in return with one better than it, or (at least) return it." There are etiquette for giving salam, including that the rider greets the walker, the walker greets the seated person, and the small group greets the large group. A husband's abstaining from initiating salam is not considered haram by the majority of scholars, but it deprives him of much good. However, his abstaining from returning salam is unanimously considered haram.