You call for a legitimate clarification. I should have said, “In charity, unless we know otherwise, we ought to assume that they are doing their best to worship and live according to the truly sacred in good conscience.” If you, knowing the truth of the Gospel, were to go off and practice Wicca because it suited you better, you would be culpable. There may be Wiccans who are similarly culpable, for we are bound to worship God in all truth as we know the truth. If a Christian were to practice Wicca in order to pursue a relationship with someone he wanted for a girlfriend, rationalizing that God recognizes the good in all who try to serve him, he would be culpable for his failure to worship God as God deserves, for his willful self-deception, and for his failure to witness the Gospel.
Having said that, our culpability, according to the Church, does not rest solely on whether we have been exposed to this truth or that, but whether or not we have been in a situation of grace that gave us opportunity to accept it. This is why practicing Wicca can be an entirely different story for a Wiccan…and this is even true of a Wiccan who was given baptism in a Christian church, if the faith handed to the child after baptism was poisoned with falsehoods, like partisan hatreds and a false version of who God is. It would be those who perverted the faith as experienced by the child who would be culpable, not the child who correctly discerned that he had been taught falsehood and rejected it.
But this is a better authority:
From the Catechism of the Catholic Church:
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.
1793 If - on the contrary - the ignorance is invincible, or the moral subject is not responsible for his erroneous judgment, the evil committed by the person cannot be imputed to him. It remains no less an evil, a privation, a disorder. One must therefore work to correct the errors of moral conscience.
1794 A good and pure conscience is enlightened by true faith, for charity proceeds at the same time "from a pure heart and a good conscience and sincere faith."60
And from the Gospel of John:
When Jesus heard that they had thrown him out, he found him and said, “Do you believe in the Son of Man?” He answered and said, “Who is he, sir, that I may believe in him?” Jesus said to him, “You have seen him and the one speaking with you is he.” He said, “I do believe, Lord,” and he worshiped him. Then Jesus said, “I came into this world for judgment, so that those who do not see might see, and those who do see might become blind.” Some of the Pharisees who were with him heard this and said to him, “Surely we are not also blind, are we?” Jesus said to them, "If you were blind, you would have no sin; but now you are saying, ‘We see,’ so your sin remains.
John 9:35-41
So here is our situation with Wiccans. We are bound by charity not to judge. Therefore, if there is a reason for which they are not culpable for what would be a grave sin for us, we still have to assume they could be in the position of innocence. We may not condemn them. We are still bound to preach the Gospel to those who worship in sincerity but in ignorance.
But note what the Catechism points out: that one of the barriers to accepting the truth can be the bad example of others. We cannot preach the Gospel if we don’t live the Gospel. The believability of a statement rests in part on the credibility of its witness. If we don’t live the Gospel, if we do not put love of neighbor before all else, we hurt the credibility of the Gospel. Therefore, we have to preach the Gospel without denigrating anything in the spiritual life of the person we preach to
that they know correctly to be good. If we condemn that which they already understand correctly to be good, in this case their desire to serve the good that they see is unquestionably in the universe and reaching out to us in the human condition, then they are not going to believe we know anything about bad and good.
This is why we must always recognize the good God put into others. If we do not, our preaching is far less likely to come to serve God’s ends and bring them to Christ.
We may sometimes be bound to seek what may be good and what is false in Wicca, if we need that to speak in love and truth to them. How can one teach, if one decides to remain ignorant of what truths and what misconceptions are in the person they would teach, or if they are too arrogant to think a non-Christian open to the Holy Spirit might have been given a grace that we, in our known sin, were too obtuse to pick up on?
Now, there are far too many religions in this world to investigate all of them, and some of us are too weak in the knowledge of our own faith to be apologists just yet, so we can only do our best, too.