So I was browsing /r/syriancivilwar when this came around:

np.reddit.com/r/syriancivilwar/comments/3mzm7k/if_isis_are_exbaathists_and_assad_is_a_baathist/

The op is asking why ISIS is trying to topple Assad's regime if they are made up of ex baathists. Most of the responses take note that "Ex" is the key word, but go on to state the conflict is due to things like Baathism being a weak ideology or having to originate in the Assad and Saddam conflict.

Now, maybe Assad and Saddam conflict holds water for former Saddam personnel in ISIS that are still baathists at heart, but we should consider that many in ISIS were never baathists to begin with and are joining for separate reasons.

I consider that thread bad politics because it all ignores the elephant in the room about the disparity of Baathist and Islamist ideology. (Only one comment mentioned this).

Baathist ideology is based on pan arab nationalism and is officially secular. There are numerous baathists who are Christian in the Middle East (or an entire different religion), while Islamism is a religion based ideology that is focused on one's beliefs rather than one's race.

Now obviously there is more to Islamism and Baathism than what I mentioned, but the main reason for conflict is the fact that one ideology is officially secular while the other is based on religion. As ISIS is an expansionist theocracy, secular or non (their version of) Salafi governments will of course be targeted regardless of their ideology, hence their conflicts with the non ba'athist Kurds

There have been instances where baathists align with islamists since most arabs are muslim, but it doesn't change the fact that Islamists like ISIS will be overtly hostile to any secular ideology. Both ideologies originating in the middle east or ISIS members once sympathizing with Baathism mean squat.