Referring to a Person as being ,Haram

Question :

When a person does something teh treme that is deviant or something that goes against the Shari'ah, many people call him "Haram." Are they sinning when they call someone by this name or are they blameless in doing so?

Answer:

If a person does something that is indeed unlawful such as fornication, and then people say about him "Haram" meaning it is unlawful for him to fornicate, then there is no harm in people saying that. But if a person does something that is not unlawful, then it is forbidden to use the word Haram to describe him here, because doing so might confuse between what Allah made lawful and unlawful in His decree and will, since by their labelling it unlawful they mean Allâh willed it to be such. This is because something could have been prohibited by Allah's will, or in His Shari'ah. So what is related to Allah's actions, then it is prohibited by His will. What is related to the Shari'ah, then it is prohibited in the Shari'ah sense, but the prohibition that results from Allah's will is not up to anyone to decide, rather it is up to Allah Almighty to decide. He is the One who does what He wills; what He wills to occur, it occurs, and what He wills not to occur, it does not. So my view is that this phrase be avoided as much as possible. Even in case where they use it to mean something that is correct, when it is assumed that something is likely to occur, or not likely to occur, it is still, in my view, a statement that one should stay away from.

Source:
Ibn 'Uthaimin
Fatawa Islamiyah, Vol. 8 Pages 324-325