Is it impolite to tell a relative or friend something bad that someone else has said about them?

Someone in my life has been doing this to me, and I can’t decide whether I should take it as a heads-up or assume that the person enjoys spreading gossip and creating dissension. This person claims that s/he is trying to help, but it makes me wonder if s/he agrees with the nasty things that the other party is saying. II believe that if you want to support someone, be a true friend and try to lift him/her up, not bring him/her down by repeating insults that detractors have made. But maybe I have the wrong perspective. So how would you take it if a friend or family member did this to you? Would you be thankful for that knowledge, or would you think that the other person is merely participating in the gossip chain for his/her own pleasure?