The Freikorps also went and fought (ostensibly) against the Communists in the Baltic states, although by what I've read of it what they were out after was some sort of "Greater Germany" idea. The local "White" forces were fully aware of this little detail, but weren't exactly in a position to refuse any help they could get even if they full well knew they'd well might end up having to fight the Freikorps themselves once the Reds were dealt with.

AFAIK the sorts of people who signed up into the Freikorps can be summed up as "embittered war vets with few future prospects, nothing better to do, and right-wing political leanings." Angry young men with nothing to do are a troublesome element anywhere. These happened to be ones brutalized by years of the hell of trench warfare to boot...

Side note: the Nazis later nicked a whole lot of details from the Freikorps.