I find it very useful to have a shared set of terms, a shorthand to describe the things we see often. I think that to a large extent, the negative connotations of the terms come from the fact that the concepts themselves have negative connotations.
For instance, when an experienced poly person hears "m/f couple looking for a single female to love them equally" they are likely to think "trouble" -- and rightly so, all too often. Similarly, when polyfolk hear "the agreement between this m/f couple is that the female may have one or more other female lovers but no other male lovers" they are likely to think "the male half of that couple is likely dealing with issues of jealousy, fear, and/or insecurity," and, again, that often turns out to be correct (that was exactly why Davis was ok for some time with me having sex with Gia but not with Eric, he admitted himself that it just made him feel insecure and scared for reasons that he didn't fully understand, and I was happy to cede that to him until such time as he got over it). So, why should we abandon the terms just because they have negative connotations when the connotations derive from the nature of the things they describe, which are real and prevalent and problematic?
As for the negative connotations of the terms expressing an underlying assumption of a preference for heterosexual relationships over homosexual ones, I actually see it the opposite way. The desire for OPP (the concept, not the term) seems to me to often come from a place of heteronormativity, in that a man may find it less threatening for his female partner to have other female partners because relationships between two women aren't "real" and won't possibly pose a "threat" to the preexisting heterosexual relationship... like, I can't help but wonder when a man wants OPP if he's thinking, probably unconsciously, "my wife won't run off with *her*, she doesn't even have a penis, whereas a penis-bearing man could steal her away!" So, OPP often makes me twitch because I wonder if that's where it's coming from. It's never occurred to me that OPP is bad because it denies women their god-given right to lots of penises, hardly. Many women in heterosexual relationships don't, in fact, have much/any desire for penises other than the one belonging to their existing partner. But if that's the case, why the need for a rule about it?
Are all couples seeking a third naive and myopically focused on their own needs? Absolutely not. Are all m/f couples that are open to women and not men working off of the male half's fear of other penises? Of course not. But it happens a lot, so, yes, people in those situations do often end up having to explain themselves.
That's unfortunate for them, and I think that in all fairness we *should* be careful about how we use those terms. We shouldn't mistake a woman in an existing m/f relationship who says "I'm interested in new relationships with women but not men" for someone operating under an OPP rule. There is every reason to believe that's her decision. But if her situation is actually "I'm interested in men and women but have chosen to focus exclusively on relationships with women because that's what my male partner is comfortable with and it also happens to be what I'm more interested in", well, there are shades of grey there that include catering to one partner's fears/insecurities (what else does it mean for the man involved to be "comfortable with" that arrangement but not with one that did allow for other men?) and some people may see a problem with that. For others, it may signal that the female half of the couple is sensitive and compassionate to her partner's needs. But either way, if it would not be ok for the woman to have a relationship with another man -- if that would be breaking a rule or a boundary or an agreement or whatever -- then isn't it, in fact, a policy that stipulates that there shall be no men (who usually have penises) beyond the man in the existing partnership? Isn't it, in fact, a one-penis policy? Sure that sounds flippant, and sure there are negative connotations, but again I believe the connotations come from the concept, not the term, and people have developed those negative connotations based on what they've seen and read about, so they're not in any way necessarily unfair connotations.
The problem comes in when we use these terms as weapons, rather than tools. When we pre-judge without knowing the facts, or when we assume unhealth to be a given just because a relationship has taken a particular form. Do the terms make that easier? Yes, probably... after all, it's easier to unthinkingly toss off a term than it is to thoughtfully analyze a situation. But that doesn't mean the terms themselves *are* the problem, or that identifying a rule as OPP is always meant to be derogatory or dismissive. Rather, I see it as quite straightforward and descriptive, in and of itself. Again, it's all in how it's used. "It seems you guys decided that an OPP is the best way to move forward -- was that a mutual decision or a unilateral one?" is very different, after all, from "Oh, I see, OPP, how unevolved, you poor thing." We also need to be willing to believe women when they say "this was a mutual decision" or even "this was *my* decision" and not use the negative connotations of the term to badger then into admitting that something is wrong. That's just plain rude.
Unicorn-hunting is an interesting one. To me, it by definition describes a couple that is looking for something that doesn't exist, that is seeking a fantasy woman without needs of her own who is capable of perfectly equal love. If a couple is open to putting another woman's needs on the same plane as their own (to me, this includes not demanding exclusivity off the bat... though they may all mutually decide that exclusivity is what they want, which is different), and are willing to see her as a complex person who will love different people differently and who may well want/need different things than them, then I don't consider that unicorn-hunting.
Should people be pre-judged, informed that they may well be unicorn-hunters just because they outwardly present as such? Well, the fact is that any bi woman they might approach will probably do just that if she has any experience in poly at all. So, I don't see introducing them to the term as mean, but rather as a reality call -- "whether or not this describes you ( and does it, by the way?) you should be prepared to overcome this preconception." Again, this is not the term's fault, it's the fault of the concept and how it is applied by far too many inexperienced couples. And, again, the negative connotation is there in terms of heteronormativity for the same reason that it is in OPP (unicorn-hunting naturally incorporates OPP).
I do worry that the terms come off as condescending and thus keep people from listening to what's being said, which is unfortunate. For advice-givers, therefore, I would especially recommend using the terms judiciously and carefully. I think I myself have been guilty of tossing "unicorn hunting" at a new poster on at least one occasion in a way that was accusatory rather than constructive, and I regret that.
But drop the term wholly? No, I think it does a great job of light-heartedly capturing a problematic mindset that needs to be called out.
Tl;dr version: terms don't insult people, people insult people.