The Order

[Treewyrm]

About attacking 'infested people'.. I don't really know.. Keepers do the same thing.
So, two greatest enemies going around shooting common enemy? Not gonna sound good.
It's either infested = Keepers won't shoot at it,

or it's Nomad weaponry gained by killing Nomads = Order won't shoot at it.

There is a bit of misinterpretation as regards the logic behind. For Keepers - they are eliminating those who carry nomad tech or items of importance (currently artifacts) to prevent humans digging deeper into the secrets of the Nomad technology. Integration and prolonged usage of nomad weapons on human ships might lead to unexpected effects (there is interesting yet disturbing story in works about it by one of the faction members). Perhaps Order knows that and would seek to remove weapons for sake of holding the infestation at bay, perhaps by asking or, if all negotiations fail, by force. So, there is no common enemy, not even a common goal, just the results tends to happen to be the same.

Cannons and Blasters are gained by killing Nomads, you cannot buy them from a base. The fact that Nomad capital ship turrets are happen to be sold at Primus and Gammu is but a mistake, they should be drop items as well.