It’s not hopeless, if you are sincere and consistant they well grow to respect you, and change themselves.
The best idea i could suggest is to change the subject with some interesting news or comment or question directed at the speaker. Like… did you hear so and so had a boy? or where did you put my tennis racket. usually this changes the subject, but if the person is infected they usually will turn that topic within 1 min to another lashon hora comment.
The best thing to do at that point is to just leave the room, go wash your face, or get a tissue, or just go for a walk.
I cannot begin to tell you the S’char one gets for avoiding L”H
and the pain, suffering, and tragedies they spare themselves and the rest of Klal Yisroel. If there is anything important to focus on now it is just that. It will make a person more sensitive in general and protect them from doing other sins as well.
Hatzlocha Rabboh!