Tabarra

wa alaykum as salaam wa rahma!

It says in Al-Mukhtasar al-Mufeed:

Being at enmity with the enemies of Allah from amongst the disbelievers and openly disobedient, is a religious obligation. This means the will of causing damages to them, and to keep the goodness and benefits away from them.

As for cursing them, it is up to you. I don't know of any reward mentioned for doing so. 

And Allah knows best!

IRS