Imo a person becomes unkind when they don’t tell the truth, I don’t believe it’s unkind to speak the truth in love.
The Lord Jesus is the perfect example of how to speak the truth in love. Please read the following comments He made;
37 “I know that you are Abraham’s descendants, but you seek to kill Me, because My word has no place in you. 38 I speak what I have seen with My Father, and you do what you have seen with[l] your father.” 39 They answered and said to Him, “Abraham is our father.” Jesus said to them, “If you were Abraham’s children, you would do the works of Abraham.
40 But now you seek to kill Me, a Man who has told you the truth which I heard from God. Abraham did not do this. 41 You do the deeds of your father.” Then they said to Him, “We were not born of fornication; we have one Father—God.” 42 Jesus said to them, “If God were your Father, you would love Me, for I proceeded forth and came from God; nor have I come of Myself, but He sent Me.
43 Why do you not understand My speech? Because you are not able to listen to My word. 44 You are of your father the devil, and the desires of your father you want to do. He was a murderer from the beginning, and does not stand in the truth, because there is no truth in him. When he speaks a lie, he speaks from his own resources, for he is a liar and the father of it. 45 But because I tell the truth, you do not believe Me. 46 Which of you convicts Me of sin? And if I tell the truth, why do you not believe Me? 47 He who is of God hears God’s words; therefore you do not hear, because you are not of God.” John 8:37-47