I always try to say something nice about anyones projects, since mine may not be to their liking either.
However, I do have a problem with someone trying to pass off someone else's work as their own. I have seen this done at a quilt show and know for a fact that this person did NOT make the one quilt that they were saying that they did!! The quilt that they DID make, not all the fabric was caught in every seam. :( I really felt bad for her, until I saw her and she said "how do you like this quilt that I made?" I could tell that her ex-mother in law had made it. I saw the ex-mother in law making it. How sad for this person that she would try to do this. :( I DID however have nice things to say to her. In private, I told my DH what she had done but would never say anything bad to anyone about their work.