Answering a question from Br Saeed Qureshi.
Shi'ahs hate the first three caliphs calling them as GHASIBEEN (Usurpers) and their books are loaded with Hazrat Ali and Hazrat Fatima shown extremely displeased with them.
Shi'ahs will consistently deny the Umm Kulsoom marriage with Hazrat Umar but it is reported by "Imam" Tabari in his 13 volume history book TAREEKH-IL UMAM WAL-MULOOK.
They especially hate Hazrat Umar since he stood as a strong barrier between Islam and the Persian conspirators. The conspirators assassinated Hazrat Umar through the Zoroastrian Feroz Abu Lulu who was apprehended and killed on the spot. This man has a glamorous symbolic mazar in Qum, Iran where he is honored as Baba Shuja'.
May Allah bless you Sir!