Is it permissible to boycott a neighbor who harms their neighbor by sitting in front of their house, smoking shisha, and having men and women intermingling, and is one obligated to offer them greetings of peace, and what is the optimal course of action in this situation?

Among the etiquettes of sitting in public thoroughfares is what has been brought forth by the authentic Sunnah (definition). And such behaviors — which cause harm to neighbors — emanate only from someone heedless or ignorant. When inviting to good and enjoining what is right and forbidding what is wrong, one should observe the guidelines and adopt the approach through which advice will be effective. One can seek assistance from those who have influence over them. If they do not desist, then they can be threatened with having their matter reported to the responsible authorities, or be boycotted if it is hoped that this will be a deterrent for them, as boycotting depends on what serves the greater good. Attention should also be paid to the danger of intermingling between men and women, and to smoking shisha or other forms of tobacco.