I recently saw another piece about how Iran supports Shia insurgents and militias in other countries, and it was portrayed as seeking to grow influence, as offensive against other countries et cetera.
It felt like Cold War all over again. During the Cold War, the Soviet Union was painted by the U.S. as evil central when it supported "communist" insurgencies in Africa. The CIA played the counter-force, supporting governments against this subversion.
In the end, history books treat those insurgents more as anti-colonialism freedom fighters and anti-racism freedom fighters than as "communists", though their later governance wasn't exactly exemplary. The U.S. wasn't only losing - it was on the wrong side of history, and its conservatism in favour of oppressors was exploited by the Soviets who gained influences because they picked the low-hanging fruits of siding with well-motivated rebels.
Nowadays Iran is backing Shia forces in Arab countries.
In Yemen, they support one tribal group just as Saudi-Arabia backed tribal groups and bribed factions for effectively controlling Yemen's politics and policies mroe than any Yemeni faction. Crime, corruption, poverty and poor governance motivated and motivate people in Yemen to rise up in arms; the Iranian-backed faction happens to be the most successful of them so far. Saudi-Arabia now bombs and intervenes in Yemen directly in order to cut back a faction they cannot bribe.
Hezbollah in Lebanon is internationally known for skirmishing with Israel, but it's also a local de facto replacement for the dysfuntional and weak Lebanese state. Much of the Iranian support is used to provide public goods and even welfare transfers for the people in Southern Lebanon, which in turn are loyal to Hezbollah. They also helped Assad in the Syrian Civil War, but this has after severe losses largely shrunk to an effort to secure the Shia minority there and notably involved some combat against ISIS.
Iranian support for Shia group in the other Arab countries such as Qatar is tricky; on the one hand armed resistance there is perfectly legitimate consideering the nature of those governments, on the other hand those groups are (close to) terrorists becuase the system of oppression in these states is effective enough to limit their freedom fo action to a terrorist's repertoire.
Let's look at the Arab states in the Gulf area as what they are: Kleptocrat 100% corrupt absolutist monarchies of fake dynasties made up only a couple decades ago. Also, they're discriminating and oppressing the Shia as people and as a religious group.
Armed resistance against those states, their leadership, their military, their paramilitary, their police and much of their judicial bodies and unarmed state groups of oppression (religious police etc.) is legitimate.
I emulated a pro-Iranian perspective* to point out that once again, judgment about who's the baddie and who's doing legitimate business depends on the perspective. Sadly, the U.S. backing for many dictatorships in the Mid East risks repeating embarrassing and tainting Cold War episodes. Even more annoying to me personally is how easily the propaganda appears to shape public opinion in the West into a perspective biased in favour of the Gulf dictators and the backing U.S..
We should rather recognize that the Mid East is a mess in general with many illegitimate governments with whom we still deal in the U.N. general assembly, but who neither deserve respect nor support. We might have sme actually advantageous influence on Iran if we had enough relations with them to threaten with a withdrawal of advantages - this way we might motivate them to limit their support to non-terrorist, non-harrassing groups or to exert respective influence on worse groups. We already used all those options to bully them into giving up their 'we could turn into a nuclear power' status instead.
To pretend that Shia resistance to established dictatorships is illegitimate and Iranian support for such resistance is 'eviiiil' equals falling back into primtive Cold War reflexes with a good/evil view of the world. That view never served us or others well.
*: Many more details could be added, many of them disadvantageous to the Iranians. This doesn't matter - I wrote this to point out that there's a substnatial pro-Iranian perspective at all.