If his intention is to call for Islam by telling the truth and informing them that Jesus is not the son then it is permissible,
But if it is just to say things that please them then it is not permissible.
If his intention is to call for Islam by telling the truth and informing them that Jesus is not the son then it is permissible,
But if it is just to say things that please them then it is not permissible.