The fact that Iran themselves admitted it, and so has the IAEA. You can hate on Trump all you want but this is without dispute. If they weren't trying so hard to create nuclear weapons, they'd surely agree not to.

I notice no one addressed the issue of them killing 40,000+ of their own citizens.

Iran is a sovereign nation. Many such are killing tons of their civilians. South Sudan comes to mind instantly. Many sovereign nations have killed that many or more of their own citizens, Myanmar and Cambodia for example, and the USA has not intervened. Part of Trump's campaign promises related to the USA not being the world's policeman, this issue strikes me as another propaganda red herring.