This is true but is only one part of what the Church says about the conscience.
(CCC 1790) *“A human being must always obey the certain judgment of his conscience.”
*That same paragraph goes on to say, however,:
*“Yet it can happen that moral conscience remains in ignorance and makes erroneous judgments.”
“This ignorance can often be imputed to personal responsibility. … In such cases, the person is culpable for the evil he commits.” *(1791)
So, while we are commanded to follow our conscience we are also warned that our conscience can be wrong and that we may be held accountable for acting on a wrong conscience. Oh, and some of the reasons for error are:
" … assertion of a mistaken notion of autonomy of conscience, rejection of the Church’s authority and her teaching … can be at the source of errors of judgment in moral conduct." (1792)
We reject the Church’s teaching at our peril.
Ender