Most of us have experience with friends or relatives say or do stuff that annoys you even when they don't intend to.
But you know that their behavior has to stop.
And you know you'll go insane if you don't say anything.
And you don't want to tell them off in front of everyone, partly to save them from embarrassment, partly to save everyone else the trauma of seeing friends/relatives arguing!
Me, I'd rather just send a letter or an e-mail telling them how I feel about their behavior!
Telling them from a distance usually gives them time to think before they react. Whereas telling them in a face-to-face conversation gives them time pressure to react now, which can cause you or them to say something they might later regret.
I have just sent a letter to someone in my family. It'll probably be in his/her mailbox today. He/she probably read it by now!
It is a very serious topic and I want that person to get his/her act together before we meet again! It's at the point where I am telling that person "if you keep that up, I will boycott any gatherings in which you are present". Yes, it's that bad!
I have sent similar letters to other people over the years. It's never comfortable to do so.
It never gets easier, but it just has to be done!