Is that the only reason? Do you believe we have obligations to other human beings who are suffering simply because they are human? If so, what is the extent of that obligation? Also, my country is more directly involved in these countries, we supply the Israeli military, so when they committed recent atrocities in Gaza, I am a part of that because I pay taxes, but even if I didn't I would still feel sympathy and want to help. We are also rather intimately connected with Saudi Arabia, which makes Iran look secular and moderate by comparison, stoning people to death is like a national sport.
I don't think theres' any reason to think Iran is any direct military danger to it's neighbors, but you're point about harboring extremists may be quite valid, thats' unfortunate. I have made several posts on my disdain for religious extremism, religion in general. However, I also want to reiterate, as Americans the situation is unique. Our government turned a pro-western democracy into a fascist nightmare, the religious zealots were the only ones left because the stable secular leaders were executed or exiled.
That responsibility complicates the issue, although sadly it often goes unrecognized.