A strictly Catholic argument against such a false view.
OC, I think
1756 It is therefore an error to judge the morality of human acts by considering only the intention that inspires them or the circumstances (environment, social pressure, duress or emergency, etc.) which supply their context. There are acts which, in and of themselves, independently of circumstances and intentions, are always gravely illicit by reason of their object; such as blasphemy and perjury, murder and adultery. One may not do evil so that good may result from it.
and I think:
1790 A human being must always obey the certain judgment of his conscience. If he were deliberately to act against it, he would condemn himself. Yet it can happen that moral conscience remains in ignorance and makes erroneous judgments about acts to be performed or already committed.
1791 This ignorance can often be imputed to personal responsibility. This is the case when a man “takes little trouble to find out what is true and good, or when conscience is by degrees almost blinded through the habit of committing sin.”59 In such cases, the person is culpable for the evil he commits.
1792 Ignorance of Christ and his Gospel, bad example given by others, enslavement to one’s passions, assertion of a mistaken notion of autonomy of conscience, rejection of the Church’s authority and her teaching, lack of conversion and of charity: these can be at the source of errors of judgment in moral conduct.
and I think:
1903 Authority is exercised legitimately only when it seeks the common good of the group concerned and if it employs morally licit means to attain it. If rulers were to enact unjust laws or take measures contrary to the moral order, such arrangements would not be binding in conscience. In such a case, “authority breaks down completely and results in shameful abuse.”23
and further I think:
1907 First, the common good presupposes respect for the person as such. In the name of the common good, public authorities are bound to respect the fundamental and inalienable rights of the human person. Society should permit each of its members to fulfill his vocation. In particular, the common good resides in the conditions for the exercise of the natural freedoms indispensable for the development of the human vocation, such as “the right to act according to a sound norm of conscience and to safeguard . . . privacy, and rightful freedom also in matters of religion.”27