First of all, I love Iranian culture, especially Iranian films, which, despite being "censured", are just beautiful.
So, I would like say that it is just that we are putting sanctions against Iran and the only reason is because of oil. If you didn't know, 17% (!!!!) of the world's oil passes though the Strait of Hormuz, which is between Iran and UAE. The only thing stopping Iran from controlling the strait is Israel and other middle eastern allies of US, who can launch an attack on Iran probably within a day.
Since Iran has made threats to blow Israel off the face of earth, and since Iran have nuclear capabilities (weapon or not), I would logically say that a sanction is the most logical step to prevent any further conflicts.
Now of course you can say that we're evil or whatever, but you can't imagine how important oil is to western civilization, not because Saudi oil is the only source of oil in the world, since Canada actually provides more oil to US than any other countries, but because cutting off middle east oil supply would mean a sudden price inflation which will instantly cripple the economy of the western world, which will soon reach global proportions.
So in summary, the logic is quite simple: kill or be killed. Sorry to scare you like that, but this is what I think of the sanction.