Here is a Yenta Truism that I believe in whole heartedly and would like to share with my vast audience and fan base and seekers of assistance. Because the application of this truism will save you many hours of anguish as you wonder to yourself, "should I inform XXX that YYY is a flaming asshole and I just don't approve of their relationship?", providing this free information to you as a benefit of visiting my site might get more people in coming here for my "free offers".
So here is the truism and the logic behind it. Truism: The world already knows that YYY is a flaming asshole and you can take it to the bank that XXX has already been informed, one way or the other, that their judgment of YYY is piss poor and they are suppressing it because their need that drives them into this relationship is pathological and one of the downside attributes of their personality which is why they deny to themselves by "overlooking" or "chosing not to give much thought to" the assholery of YYY, putting friends and family in the unenviable position of having to wrestle with themselves as to whether they should admit directly to XXX that they hate YYY with a passion and fear for their loved one's future sanity (and their own should they be forced to interact with YYY as a condition of interacting with XXX).
So your good friend has been dating a fucking dick. You hate his fucking guts, and everybody who has met him talks about him behind your friend's back and you feel guilty, should you warn your good friend? Reality: your friend, unless she is blind, deaf, dumb and living on Planet WhattheFuck KNOWS THIS. She is just crossing her fingers that you haven't noticed. All you need to do is indicate subtly that YYY is a fucking dick by rolling your eyes or saying VERY LITTLE and when she comes to you for advice, for example, if fucking dick doesn't consider her schedule, as an example, say something like, "well, it doesn't surprise me. He isn't exactly the most considerate person I've ever met" and go on from there. By no means encourage the relationship.
Family members require a little different handling. Dead silence should accompany any mention of YYY's name until you drop the first bomb stating "Do you REALLY want to hear my opinion? You should hear my opinion and I've been holding back giving it to you because I had HOPED you would have FIGURED IT OUT ON YOUR OWN but you haven't so let me tell you it shocks me that you haven't noticed that YYY is a fucking piece of shit" or words to that effect. More aggressive language is required because family alliances tend to infiltrate the whole family and turn family matters into a tailspin. Trust me, I have 30 years experience with the biggest fucking loser in the world wrapping her gnarly tethers around my family's prior sense of well being. See you next tuesday, so to speak.
So please let me know if you need any further elaboration on my truism. I will also update this as the spirit moves me.