You lost me at "hoarders".

 So my stamp collection is a sign of mental illness? And what do we make out of the cosplayers with extensive collection of plastic figurines and the like? Mental illness too? And car nuts - are they "crazed" road rage prone accidents waiting to happen? Cat ladies? People with a wine cellar? People with porcelain figurine collections?

 Just limit what types of guns can be purchased/owned, add ownership restrictions - and stop there. Don't turn this into another witch hunt.