History of al-Tabari, Volume 9 page: 186- 187
Iqd al-Fareed, by Ibn Abd Rabb, Part 3, Pg. 63
"When Umar Came To The door of the house of Fatimah, he said: "By Allah, I Shall Burn Down (the house) over you unless you come out and give the Oath of Allegiance (to Abu Bakr)."
History of Tabari (Arabic), v1, pp 1118-1120
History of Ibn Athir, v2, p325
al-Isti'ab, by Ibn Abd al-Barr, v3, p975
Tarikh al-Kulafa, by Ibn Qutaybah, v1, p20
After all these referrences is there any other proof needed to show that Umar was the bitterest enemy of Ali and Fatima.
Now Sunnis you decide what is important for you.
To be with Ali or Umar!!