I used to run the 3D printing community on G+ at around 500k strong, (about 10k weekly active users according to Google's stats) and I ended up actually pissing off a lot of my European users because of this. My viewpoint on it, was as an engineering exercise -- it's an amazing thing. It's not advocating for guns, and guns aren't only used to kill other people. So I stood up for the guys posting about their engineering challenges, and their work making 3D printed parts for a machine with high impact loads and loads of cycling issues.
Unfortunately, it lost me some friends, like Gina Haubage and Tomas Sanladerer -- as they disagreed highly; and wanted to ban anyone posting firearms related 3D printing content.