All sins can be forgiven by sincere repentance. Almighty Allah said: “Despair not of the mercy of Allah, Who forgives all sins. Lo! He is the Forgiving, the Merciful”. Yes, it is recommended to seek forgiveness whenever the committed sins are remembered but should not turn into psychological complication.
It is permissible to present the incidents of the tragedy of Kerbela without guaranteeing that it is authentically took place but rather it is based on the fact that they were written in designated books for this particular topic.
It is better that the speaker to observe various aspects especially the level of the understanding of the audience, the religious fundamentals and historical truths.