The same tabari narrates in the same Tarikh that...
The same tabari narrates in the same Tarikh that,on the day of Ashura,Imam Husain (a.s) gave a lecture before the army of Yazid,exhorting them not to indulge in blood-shed and not to kill the only surviving grandson of the Holy prophet.
At the end of the khutba, he said; "O People, if you do not like me then let me return to the place of my safety.'' Then Qais bin Ash'ath said to Husain: Why not submit to the order of your cousins (i.e Yazid and Bani Umayya), because they will not show you but what you like (they will not treat you except in a way which you will like) and no evil will reach you from them.
Imam Husain said: "You are the brother of your brother (Muhammad bin Ash'ath, the killer of Hazrat Muslim bin Aquil).............. "No by God, I will not put my hands (into theirs) like honourless person, nor will I accept (them) as do the slaves. "O Servants of Allah, "I seek refuge in my Lord and your Lord that you do not stone me' (Qur'an 44:20). 'I seek protection of my Lord and your Lord from every arrogant who believes not in the Day of Reckonning".
In view of such overwhelming evidence, one may only assume that Umar bin Saad wrote all those alternatives (without any basis, of course) just to please Ibn-e-Ziyad, perhaps in the hope that once Ibn-e-Ziyad postponed the battle and talk started, better results might follow. It is a mirror of the honesty of your writer that while he copies the letter of Umar bin Saad, he does not think it necessary to quote the rebuttal of Aqba (r.a.) or even Hani bin Thubait.
A more charitable explanation may be that the poor fellow has never seen Tarikh of Tabari, and has used the name of Tabari to impress his readers. I am not interested in the mental luxury of deciding whether Umar bin Saad was more sympathetic or not. All we care, and all that matters, is the fact that he was the commander of the army of Yazid in Karbala; and that when Allah gave him a chance to save himself from Jahannam, he refused to grasp the opportunity and plunged into the Fire of Hell.
That opportunity was given to him when Ibn-e-Ziyad wrote to him that if he was not ready to immediately wage the battle against Husain, he should hand over the command to Shimr. He did not.