Yes our Imams cursed the oppressors who murdered our Holy Prophet (s) and killed Fatima Zahra (as). All shia believe in Bara’at (denouncing and disassociating) from those unjust rulers and oppressors. This is a fundamental belief in Shia Islam, but the difference of opinion lies in Tabarra which is the action of doing Bara’at. So to be clear Bara’at is belief in the concept and Tabarra is the action of doing it. When looking at the practice of tabarra it must be done with wisdom and not to enrage or entice others. Also you have to examine the situation you are in if taqiyya is necessary or not and many other factors.