"A false conscience which is mistaken in things which are intrinsically evil commands something which is contrary to the law of God. Nevertheless, it says that what it commands is the law of God. ... one who follows such a conscience and acts according to it acts against the law of God and sins mortally. For there was sin in the error itself, since it happened because of ignorance of that which one should have known" (St. Thomas Aquinas, De Veritate, 17, 4, 3).

"sometimes the error of conscience does not have the power of loosing or of excusing, namely, when the error itself is a sin, such as when it proceeds out of ignorance of that which someone can know or is held to know, just as if he were to believe that simple fornication is a venial sin. And then, although he would believe himself to sin venially, nevertheless he would not sin venially, but mortally" (St. Thomas Aquinas, Quodlibet, 8, 6, 5).

"we have similar tensions in the Catholic Church over the same issues"

It is Koch who has tensions in his head. We have no tensions in the Catholic Church. All who have tensions on these issues are heretics, and therefore are outside the Catholic Church.

"when necessity compels, not those only who are invested with power of rule are bound to safeguard the integrity of faith, but, as St. Thomas maintains: 'Each one is under obligation to show forth his faith, either to instruct and encourage others of the faithful, or to repel the attacks of unbelievers'. To recoil before an enemy, or to keep silence when from all sides such clamors are raised against truth, is the part of a man either devoid of character or who entertains doubt as to the truth of what he professes to believe. In both cases such mode of behaving is base and is insulting to God" (Pope Leo XIII, "Sapientiae Christianae", 10.01.1890).