1. Their straight orientation will most often be a source of life-long temptation and struggle.
Although straight Christians should grow in holiness over the course of their life, they will most likely never reach a point where their orientation ceases to be a source of temptation in one way or another. So we must demand life-long vigilance against the temptation to simply do what feels natural based on their orientation.
2. Straight people have been told that their sinful lust is just a normal part of human sexuality.
If the statistics are correct, around 2% of the American population identifies as gay or lesbian. Quantitatively, then, we should expect far more problems with straight people lusting than gay people lusting. It would be good if Christians kept that 98%/2% balance when they're highlighting sexual sin. I realize that questions about same-sex relationships are going to dominate the landscape right now, but we dare not give the perception that people sinning with the same sex is qualitatively different than people sinning with the opposite sex.
3. Straight people have been told that they have to have romantic and sexual relationships to be fulfilled as people.
So we cannot affirm the common belief among straight people that romance and marriage are better than the single, celibate life. We must affirm, however, that community is necessary for the good life. And the church itself is called to be that community for everyone, married or single.
4. Straight people are constantly bombarded with images and stories of unbiblical practices of straight sexuality.
This is just one example. From magazine covers emphasizing lust, promiscuity, and sex as nothing more than technique to TV to movies, straight people are constantly and consistently being sold images and stories that are contrary to biblical teaching.
The default view and practice of straight people in our culture--including straight Christians--is likely profoundly unbiblical because we are so saturated with images and stories that form and shape us. So we dare not simply affirm the assumptions that straight people bring with them to the church.