I don't mind to see an unhealthy relationships in fiction, if they seems to be depicted and analyzed by the author honestly, with consistency and understanding. But yes, I'm very irritated, if they are presented as a "TRUE LOVE™", like, when author seems to have no understanding of their own characters, and present all shit they are doing as "LOVE", instead of making any attempt to honestly analyze and highlight their true motives through the story. I think, in this aspect we share the same thought 
As you already probably understood, in my own story I want to devote some attention to unhealthy relationships as well (and mock on some romance stereotypes, too). I also don't mind to see and write "bad" (from gray to black) characters, if I think that they are well and honestly written. In this case, I even find them more interesting than good characters, because if the characters aren't obligated to be "good", they can have more diverse personality and more complicated psychology problems.
It's a problem for me either. There were... more than one cases, when a girlfriend or a wife of my friend got jealous of him to me strongly, so spending too much time or having too much conversations with me caused him a problems. As a result, we had to drift away from each other for awhile, to not cause him more problems and not to worry his girl so much. As a result, I have to always remind myself, that I should be very careful, communicating with male friend, who has a spouse/GF, to not make her jelaous and not cause him problems... because it's so easy to make some people jelaous... 
From one side, it's understandable, that they worry about their men, when they are around me, cause I'm well-known for my... too free views. From another side, I openly claim that I will not make any attempts in the direction toward physical closeness to any close friend (and will refuse any of such a possible attempts from him, if they'll ever appear), IF I already know that he has deep monogamic relationships with a girl, who will seemingly be deeply hurt from it. I don't want to spoil a life and relationships of a people, who mean a lot to me. The sad side is... not everyone entirely believes me. 
P.S. Now, thinking about this, I think that maybe it's still my fault to some degree. It's hard to believe a person, who have deceived people before and made a decent amount of bad things toward others in the past. Even despite I didn't deceive anybody in THIS particular aspect.