To be honest, with crime dropping as precipitously as it has been, suicide is about the only argument they have left, so I can’t blame them for using it. Suicide is also a pretty big pool of grief from which a gun control group can mine funds from. Suicides affect families more broadly across the income spectrum, so not everyone affected by it has a thin wallet. This may seem cynical, but regardless of how much our opponents might really believe they are trying to usher in a better world, at the end of the day if you run any non-profit organization, bills must be paid, and paychecks written, and that means thinking about where to get money.
I have little doubt that people who commit suicide by firearm tend to be more successful than those who, say, swallow a handful of sleeping pills. But the fad among kids in my area these days seems to be throwing themselves in front of an Acela, which is probably even more sure than a gun. Indeed, that is a popular means of suicide in Japan, which has a far higher suicide rate than the United States, despite largely prohibiting firearms.