I agree with all you say and unfortunately criminal behaviour (in the case of firearms) is always going reflect poorly on the law-abiding owner in a negative way. Also, irresponsible use of firearms will do the same, people being idiots I mean. It's frustrating as with each occurrence the thumbscrews get tightened on those doing the right thing.
People are unpredictable and one who seems completely normal now (whatever that is) could change in the future. That's what humans do. It makes it it difficult to regulate the firearms (and other) situations.
I believe everyone has the right to defend themselves or those who cannot do so for themselves. You agree clearly.