Here is an article by globalsecurity.org on the MEK
The MEK was an enemy of the Shah and of the US in the 1970s. Since the early 1980s or so, it appears to be the enemy of the Iranian regime. Their strongest enemy, perhaps.
They really frighten the Iranian mullocracy.
In the list of their targets in the 1980s and since, I don’t see that they have targeted any civilians. If they are today a terrorist organization, or have been so in the past two decades, I think that we would have seen some civilian targets during that time, wouldn’t we?
They are strongly pro-American today. In their rhetoric, anyhow.