I've yet to dispute the notion that morality in general is -- or ought to be -- ultimately subjective. If you'll read my post again, you'll see that I specifically referenced personal choice as a subjective element in morality. While it's easy to cite countless moral discrepancies of varying degrees across countless eras and civilizations, that shouldn't be to imply that the notion of an objective societal moral bedrock of some sort upon which to base the contingent, subjective aspect of human choices with respect to morality isn't a worthy and noble goal, or that a sort of fundamental morality generally exists in human society, even if that bedrock -- for instance, the right to life -- carries certain, justifiable exceptions that undermine its otherwise objective stature.
In this respect, I tend to agree with you -- morality isn't entirely objective or entirely subjective within any one cultural context, but rather exists on a spectrum that the general consensus adheres to that bases a given act as generally moral or generally immoral, even if this spectrum isn't particularly similar across all cultures -- and even if it's arguably inconsistent in terms of justice and social evolution. However, this inherently suggests that morality on a broad, generalist sense is more fundamentally subjective than objective in nature, given the extent to which the capacity for reason and intuition alongside human nature is capable of being changed or molded in light of variables such as the political system in place, the general beliefs of a culture, social dominance theory as it pertains to humans, and so on and so forth to near ad infinitum.
To reiterate, this shouldn't suggest that morality has to be subjective to the point that only an anarchic philosophical template of some sort could consistently apply without suffering some form of self-contradiction. In philosophy, it's generally accepted that, beyond formal logic, it's extremely difficult -- if not impossible -- to pin a given concept or application as flatly contradictory in light of the multitude of variables and circumstances that have to be taken into consideration, many of which present their own plethora of variables to consider. Put simply, morality is a very, very complex game, but that doesn't automatically negate the value of a moral center of some kind. Our legal infrastructure recognizes this through our system of justice, as you've rightly pointed out, which exists to enforce society's general moral principles as we see fit on the basis of variables that factor into the equation of the morality or immorality of a given act or principle.
Since we're at least generally in agreement here, let's move on. You've implied that, because the LGBT movement hasn't "advanced the progress of our society in general" or "developed anything groundbreaking that will be useful to all of us," and that since it's occasionally a temporary detriment to the daily lives of commuters and consumers, and that on extraordinary occasions it's capable of leading to violence, it's somehow unworthy in some respect or another. This is a very questionable point of contention that heavily invokes utilitarianism, which in reference to social equality is generally understood to be both inapplicable and irrelevant. Were the civil rights protests of the '60s as heinous on the basis of their similarly detrimental effects during protests? Did violent disputes that often erupted as a result of these protests undermine the overall goal of the civil rights movement as a noble one? No? If so, why invoke utilitarianism at all in disputing the LGBT movement when moral and philosophical justifications alone should be enough to suffice? Given the size of the movement, why should isolated incidents have any significant bearing on anything? Why? You're attempting to tack on a spare tire to bolster a poor argument. In other words, you're adding fluff.
As for the slippery slope... While cultural evolution in some direction or another is inevitable, to imply that one particular political issue is capable of being legitimately coincided with a completely different issue on the prophetic, unfalsifiable basis of a fear of a "domino effect" that ultimately has an arguably negative conclusion is ridiculous. I challenge you to make anything resembling a coherent argument that legitimately, factually, and relevantly supports the slippery slope argument as it applies to LGBT equality. Considering the extent to which the slippery slope is capable of being invoked to support all sorts of restrictions on civil rights and liberties within the context of an objective morality, and given the absurd degree of variables that have to be taken into consideration when comparing X society with Y society or X policy to Y policy, I very, very sincerely doubt you can. Bear in mind that this entails acknowledging and discussing certain applications of the slippery slope, such as women's suffrage and the statistically significant gap between men and women in terms of conservatism and liberalism.
