Some have a gambling orientation. Some have a drinking orientation. Some have an adultery orientation. I have a pride orientation and an anger orientation. Overall, man has a sin orientation.
Oddly enough, we only seem to use the term ‘orientation’ as an excuse for homosexuality. I had a temper when I was a baby, I’m told. Still do in my 50s. That doesn’t excuse my temper. It just means I need to submit to God and be changed. It is also something that counseling can help.
I read a book years ago by a guy who specialized in counseling homosexuals. He said it was not genetic, but it was often rooted in the first years of life. He said it was a continuum - some chose to be homosexual, some could change to heterosexual, some would always deal with homosexual desires, on down to some who would remain active homosexuals and were glad to be that way. His counseling focused on helping those who wanted to change.
Mohler is wrong, according to this guy. I cannot speak to it from a counseling viewpoint, but I do think Mohler comes too close to excusing it when he talks about an orientation.
I disagree that Mohler is excusing homosexuality, because I think he would agree 100% with what you said about everybody having an orientation toward sin. I have read other selectons of his writings, and he is very strong on the need of the grace of Christ to break through sin-patterns which might be linked to inborn personality/temperament factors (like anger/temper!) or long habituation.