My mom made a good point to me about other similar issues...in brief, she said phrase it to sound like it is their idea, their own thought, don't tell them to do something so harshly because it comes off as rude and demanding.

My mom doesn't know about PC so I'm not saying this because I told her about this or anything.

I think the way you initially phrased it sounds like "OMG STFU I'm so sick of hearing this!"

Obviously, that's not how you want to come across.

I would say instead, "It's completely up to you, but think about how important this person is to you and why you need the help from them, and I would reconsider if the help you need is worth the problems you seem to have with this person. Either way, I'd rather not discuss this person with you any further because it's too much for me to handle."