Did they ask you for your opinion? Were you in a position of some authority over the artist or his or her work, i.e., art instructor, art appraiser, juror in an art show, admissions officer for art school? If you can answer yes to either question, then no.

Yes, I was asked as an authority. And it was truly horrible.

I stalled off for ages, but i finally admitted it.

I'd show them, but that would be worse.

Sometimes one just has to have these difficult conversations. And I think in the long run you may have done them a kindness. The mature, intelligent response to being told your work is terrible is either "I need to improve my skills", or "I just don't have the talent for this. I need to stop wasting time and resources on it and find something else I do have a talent for."

I had a mentor suggest dentistry.