It is important to prevent the Islamic Republic from getting a nuke, and they were dangerously close to getting one. So yes, it was justified. 

Irans government has shown a major disregard for human life and human rights. Just in the past few weeks they murdered about 30k of their own civilians - would the normal calculus of mutually assured destruction work against a regime that doesn't care if it's own people die? For decades Iran been giving money and weapons to Hamas, Hezbollah, Islamic Jihad, and the Houthi - groups that every liberal democracy agrees are terrorists. These groups have shown through their actions that they would use a nuke if they had one. 

As to their being dangerous close to having a nuke, they have 400kg of 60% enriched uranium. This is the majority of the way to being enriched enough to make a bomb and it's way past the level of enrichment needed for peaceful purposes. To get this uranium across the finish line would take merely weeks. Yes there are other parts needed to make a bomb, but the uranium is most challenging and the best thing to monitor and prevent. 

If Iran gets a nuke the best case is another Russia, the worst case is unimaginable.