Larry Vickers, a popular creator of YouTube gun videos, may get a prison sentence after he pleaded guilty in October to two federal crimes including a conspiracy to import illegal machine guns. But his admissions of guilt have done relatively little to dent his profile on YouTube, Facebook or any of the other internet platforms that helped make Vickers famous within the online gun community. He’s still posting updates to his fan base of 415,000 followers on Facebook while he awaits sentencing, and the hundreds of videos featuring him using various machine guns are still available on YouTube. The criminal...