If what you're saying is that it's ideological to want to separate dangerous offenders from society, then it's ideological, because those dangerous offenders, if allowed out on the street, continue to commit crimes.
One specific study indicated that for every serious offence committed by an individual who was actually incarcerated for a year, 12 other offences are not committed. That involves 12 other victims, at a minimum. So the issue is that we believe that not only does it assist in deterring that, but it specifically incapacitates that particular criminal who would choose to use a firearm.