"Can. 747 §1. The Church, to which Christ the Lord has entrusted the deposit of faith so that with the assistance of the Holy Spirit it might protect the revealed truth reverently, examine it more closely, and proclaim and expound it faithfully, has the duty and innate right, independent of any human power whatsoever, to preach the gospel to all peoples, also using the means of social communication proper to it." From a Catholic perspective, it is the duty of the Church to share the good news and therefore it is also the duty of the Church to protect it against misinformation (heresies). More specifically, the faithful who have received the sacrament of confirmation have the "power to profess faith in Christ publicly and as it were officially" (CCC 1305, quoting St. Thomas Aquinas) and the spiritual wellbeing of the faithful is the responsibility of the diocesan bishops and the whole Church hierarchy (Jn 21:15-25, per the Catholic interpretation of those verses).

Because an LLM does not have a soul and cannot receive the sacrament of confirmation it has no power to spread the gospel. Furthermore, it would be irresponsible for a bishop to approve of the use of an apologetic chatbot, even if it were only trained on the arguments of confirmed faithful, because its thinking cannot be explained coherently.

For those asking "Why does this even matter?", remember: the salvation of souls is at stake.