Asalumu Alaykum,
The role of a copy writer for a business or agency would be to write content for advertisements, emails, blogs, etc. With the assumption that the business/client is generally halal, would it be haram to write about or include in the copy things about Christmas, or LGBT etc.? Meaning, writing in favour of the haram such as saying; “Merry Christmas” or “Happy Pride Month”. Sometimes you would need to craft these ads or blogs yourself and other times your role is to just input them wherever they need to go.
Note: I am not currently working in such a role.