I doubt Kurds really care about defeating ISIS in the long run, they want to capture and defend areas that they consider part of a Kurdish homeland, which in their view is being established in Syria.
Iraqi Peshmerga is not a competent or unifed military force, and it relies alot on Turkey, while Turkey is the foremost military power in the region.
The idea of a unified Arab power is deader than ever, especially considering what's happening in Syria, Yemen and Iraq.
Ironically MEK was more anti-western than Basij during the Iranian revolution.
I seriously doubt this group matters much, it's just that they are a quite vocal group.
If anything it forces them to become more flexible more adaptable, and tougher than they used to be.
Waging war on the same enemy for too long isn't a good thing