Respect is the opposite of contempt. I have learned to give the person their God-given dignity and the respect that comes with that dignity even if they do not respect themselves. The movie The Green Mile is an example of that. There are so many in the Christian community and the world who do not respect sinners as a person. Hate and contempt consume a soul every time and destroys every relationship that they have.
Chose to speak the respect. You will not feel nor want even to simply say it, but you must! It relieves a huge burden and releases the responsibility of the response to God Almighty and He will repay with interest if the person refuses to repent.
I look for contempt when I am counseling a couple. When I see it, I know the relationship is doomed. Like finding an aggressive cancer on the liver, if there is not radical surgery and just as aggressive removal of the cancer, the cancer will consume the body. Same with contempt and the soul. If there is not radical removal of the contempt then the contempt will spread in the soul and consume the soul.
Do not trust your emotions nor even your mind in this spiritual matter. You know what your Lord expects of you. Obey Him and confess your respect of the person's dignity. It will keep you out of some dark places. May God grant you the grace of His presence as you follow Him through this valley.