Why do Sunnis have a problem with Matam?

Re: Why do Sunnis have a problem with Matam?

On 10th moharam 63 hijri Hussain a.s army of 72 fought with Yazid’s army, there were sahabis on both side armies. Hussain a.s army included ahleybait a.s too. If it is sunnat to fast on that day then all sahabis and ahleybait a.s shld have known, Tell me one person in both armies who was fasting on 9th or 10th moharam.

And kon si khushi key rozay ? ru reffering to “Islam was saved by Imam Hussain a.s” ?