According to all the history I’ve read, the SA was pretty much a bunch of veterans reacting to the commies.
I doubt it was that simple, but it was certainly a part of the issue. The common viewpoint on it today is that the Nazis attacked the Weimar Republic without provocation.
This is at best historically incomplete. At times the Commies allied with the Nazis against the Republic, on the idiotic notion that Hitler would be the Kerensky of Germany clearing the way for a Red Revolution. This notion was based almost entirely on communist theory, with no grounding at all in the actual facts.
Conflict between Nazis and Commies makes me sympathize with Kissinger’s comment on the Iran/Iraq War. “It’s too bad they can’t both lose.”