I think two things that have contributed to the perception that divorce is ‘ok’ in the Christian Church, whereas gay (same sex marriage) is not ‘ok’: the degree to which “no fault” divorce has become increasingly easier to obtain in the US and the truth that the Bible contains an exception clause for one and not for the other.
In America, one spouse can divorce the other without legitimate cause, and the other spouse is powerless to force the other to stay in the marriage. In these cases, the innocent spouse normally remains in the church and is in need of help to overcome the emotional pain and suffering from the personal rejection a divorcée experiences (thus divorce care ministries). The church must work exceptionally hard at creating a culture where traditional marriage is held in the highest esteem as a picture of Christ and the church (Eph 5:32), while at the same time, ensuring that grace flows abundantly to those left in need from the trauma of divorce. This is quite a difficult task. When one is abandoned by their spouse, he or she needs the church much like a widow needs the church, and although Paul encourages the younger widows to remarry (1 Tim 5:14), the church needs to examine each situation on a case by case basis. Every effort must be made toward reconciliation according to the Gospel and grace each believer has received through faith in Christ. The church must determine if and when the divorcée is free to remarry based on the exception clauses granted by Christ (Matt 19:9) and Paul (1 Cor 7:15). This is why there seems to be a culture where the church bashes one (gay) and accepts another (remarriage). In most cases, this is a misperception.
A few less “Amens!” when the preacher is preaching against SSM and a few more “Amens!” when the preacher is preaching for the holiness of traditional marriage could go a long way toward eliminating this misperception.