They aren't the only ones and frankly, of all the groups that horde, they are the least consequential.
I never bothered uploading and posting the pic, but I got a screenshot one night of a friendly horde and an unfriendly horde on radar. They were literally in adjacent sectors, about 20 or so planes a side, and they just flew past one another to hit the undefended bases they were going after.
It made me chuckle pretty hard. It seems base rolling in a horde is seen by many as the only way to win, and defense is considered a 'waste of time' by many.
Ah well, it is a varied and rich ecosystem that requires many types of player to create the delicate balance that is the Main Arena.
Wiley.