You placed your question in the 1920’s. The SS was founded as a bodyguard unit for NSDAP leaders in 1925 and remained purely an organ of the party until 1933 when Hitler became chancellor and the Reichstag passed the Enabling Acts. Up to that point, most of the political violence was carried out by the SA, which was likewise an organ of the NSDAP rather than the government. After the Enabling Acts, the Nazi government deliberately blurred the lines between the German government and the NSDAP, but that is well outside the timeframe you suggested.
To answer your question, I would probably not do business with any part of NSDAP starting in the 1920’s on account of their history of street violence and their platform of abolishing democracy. I would similarly refrain from doing business with the German government as soon as the Reichstag abolished democracy and outlawed every political party other than NSDAP. This would extend to the SS although the SS itself was not especially involved in any of these events.
As you can see, this isn’t a particularly relevant analogy.