Whether we accept the event of Karbala as a fact or accept the version by Dr. Shabbir stating Hazrat Hussain was martyred by Parsis, either way the great soldier the commander laid his life for a great cause guarding the Divine system ordained in Quran. You are very right. More than mourning, it is the message that,s more important.
As Dr. Allamah Sir Iqbal said,
Haqeeqat Khurafat Mein Khu Gayee
Yeh Ummat Rawayat Mein Khu Gayee