Reasons:
1. The are the primary funder of terrorism in the region. Hamas, Hezbollah, and the Houthis.
2. They were enriching uranium for no purpose other than to make nukes.
3. They are a jihadist death cult that would have used the first nuke they got to attack Israel.
4. They slaughtered 30K of their own citizens.
5. They have plotted to assassinate our president. (I'm sure you won't care about this one)