I think you are right and not right.
Homosexuality is a sexual sin, no better or worse than other sexual sins such as fornication and adultery and using prostitutes.
But, the New Testament is very clear that for a Christian to engage in sexual immorality is a very serious sin, because the Holy Spirit cannot be present where there is sexual immorality. Sexual immorality will not only destroy an individual spiritually, it will also destroy a church body that embraces (or doesn’t enforce Biblical standards on) sexual immorality.
The other problem, which you make reference to, is that if you tolerate one type of sexual immorality, you tolerate them all. Thus, one can say the present problem with homosexuality has its roots in the church turning a blind eye to fornication and no-fault divorce (serial adultery).
And a good example today is the PCUSA. In its rush to validate homosexuality for ministers and elders, it threw out all standards that ministers and elders must be chaste in singleness and faithful in marriage. Thus, not only can someone qualify to be a minister in today’s PCUSA if they are a practicing homosexual, they can also qualify if they are having heterosexual sex outside of marriage or cheating on their heterosexual spouse.