Oh, please.
Conscience is not, in and of itself, the sole rule. If it were, then you must excuse any evil if it were done according to one’s conscience. Was Hitler acting according to his conscience, and rightly so? If so, then I guess you are right, it is “End of story.”
You skipped the intervening paragraphs. Pay special attention to 1783:
1783 Conscience must be informed and moral judgment enlightened. **A well-formed conscience is upright and truthful. It formulates its judgments according to reason, in conformity with the true good willed by the wisdom of the Creator. The education of conscience is indispensable for human beings who are subjected to negative influences and tempted by sin to prefer their own judgment and to reject authoritative teachings. **
So it appears it is more than just obeying conscience. One must have an informed conscience. Conscience, in and of itself, is not enough. One must apply reason as well.
1784 The education of the conscience is a lifelong task. From the earliest years, it awakens the child to the knowledge and practice of the interior law recognized by conscience. Prudent education teaches virtue; it prevents or cures fear, selfishness and pride, resentment arising from guilt, and feelings of complacency, born of human weakness and faults. The education of the conscience guarantees freedom and engenders peace of heart.
The formation of conscience is not something that is static. Our conscience must always be continually informed, and we must continually seek the truth. We cannot be content to sit on our conscience as it is now without any effort to conform that conscience to the divine will.
1785 In the formation of conscience the Word of God is the light for our path,54 we must assimilate it in faith and prayer and put it into practice.
We must also examine our conscience before the Lord’s Cross. We are assisted by the gifts of the Holy Spirit, aided by the witness or advice of others and guided by the authoritative teaching of the Church.55
When one considers how their conscience informs them, one must always consider whether it conforms to the divine will. If not, then why not? If not, how do I make it so? I would question a conscience that leads me to support politicians that support the slaughter of innocent, unborn children. Does such a conscience conform to the divine will?
1786 Faced with a moral choice, conscience can make either a right judgment
in accordance with reason and the divine law or, on the contrary, an erroneous judgment that departs from them.
Note here that any decision made from conscience may be right or wrong in judgment. And that only a right judgment is “in accordance with reason and the divine law.” Note the key word:
reason. Conscience, by itself, is not a guide.
1787 Man is sometimes confronted by situations that make moral judgments less assured and decision difficult. **But he must always seriously seek what is right and good and discern the will of God expressed in divine law. **
Regardless of the difficulty of any such decision, one must always try to align one’s conscience to God’s will. Sorry, but I fail to see how the support of pro-abortion politicians is aligned with God’s will.
The final point is twofold: 1) the right application of conscience presupposes a well formed conscience, and 2) conscience is not the sole basis upon which we are to base our actions.