While a single poll, it is interesting longitudinally because it tracks the same questions from 2006 to 2010. It is noteworthy for the fact that, for the first time, the majority of Americans, taken together, consider such relationships "morally acceptable." It is even more noteworthy, IMO, for the fact that this change is a product of a huge shift in opinion by men in all age demographics. The view on such relationships by women of all age demographics remains relatively stable. Even more interesting, the shift in men's view jumped significantly between 2009 and 2010.
Indeed, in the two age demographics provided, more men than women now consider such relationships morally acceptable, although the difference is not statistically significant. But it is astounding when considering that between 2009 and 2010, there was significant movement to "morally acceptable" among men of both groups, flat growth among women ages 18-49, and actual reduction of 1% for women ages 50+.
The op ed postulates three theories for the shift: rising egalitarian trends among men generally (although why this should be is not adequately explained, but it's just an op ed), greater exposure to openly gay couples and individuals, and a fear that express homophobia may indicate homosexual tendencies. This last may actually contribute to a "Wilder effect" where men have not actually shifted their attitudes, but prefer to state a more favorable opinion to pollsters.
I would add same that sex marriage and same sex relationships received enormous news coverage in 2009-10. This may be a subcategory of the "exposure" theory. But I think it's more than just exposure. The debates around same sex marriage and ending Don't Ask Don't Tell are encouraging individuals to actually examine underlying assumptions at a time when a variety of circumstances is making it ripe for them to do so. But this also does not explain the disparity between men and women in terms of overall change in opinion in the last several years unless we postulate some sort of natural ceiling/threshold for moral acceptance which men have now reached. But this is profoundly unsatisfying because there is no evidence or theory to explain this.
It would be interesting to know if there are other, similar social norms where there has been a dramatic shift in opinion in one gender but not the other.