Yeah, I can't remember the whole story, but the designation of borders between Iraq and Iran has been a sore spot ever since the post-WWI days. I think Iraq/UK tried to set the border up on the eastern shore of the Shaat al Arab waterway, which would mean Iranian vessels would have to pay a fee and be subject to inspections in order to reach Iranian ports inland, and Iran wanted the border to be drawn down the middle fo the waterway instead so both sides could use it. I may have it backwards, but I know this is one of the things that drove the Iran-Iraq War of the 1980s.
It's easy to paint Iran as the bad guy all the time, especially if you remember the hostage crisis of 1979. I was in elementary school when it happened, and it certainly won Iran no friends in the U.S. But as you point out, the situation's much more complex. In many ways Iran is the way it is today as a result of US and UK meddling back in the 50s and before.
I just ask that when you see an incident like this in the news, not to get all spun up and emotional about it. Look at the background and think carefully.