Props for the debate - it's a good idea.
Broadly I agree but in the devil's advocate tradition, one could argue that guns do serve a civilised purpose in society for the purpose of food production, land management and even security.
A - Food production
Very few reasonable people who are familiar with large-scale livestock management and slaughter would describe the practice as "civilised."
Between forced insemination, the mass-hatching yet systemic discarding of male chicks and the stressful abattoir process, the system is dire in need of reform. One potential option here, an eco-friendly one at that, would be a return to the hunting tradition.
B - Land management
Unpopular a view though it can be: sometimes population surges of deer, rabbits, badgers and grey squirrels (to name but a few) can cause substantial damage to our ecosystems. Whilst poisons can be an alternative, they act indiscriminately and could be considered wasteful as any meat yielded from the process would be spoiled by contamination from the toxin.
C - Security
First off, in any many countries, there are dangerous wild animals such as bears in the US and Canada, big cats in Africa etc. For rural areas to be safely visited/inhabited, one could argue a gun is necessary. Closer to home, however, civilised societies can only remain such if there are means of protecting the public from dangers/threats to their civilisation. Unless we can ensure that no individual is going to pose a violent threat to large groups of people using weapons, which we've now unfortunately learned includes vehicles, then there will always be a legitimate utilitarian argument that guns are useful tools for bringing those situations to a speedy end and minimising loss of life.
Would love to hear what others think!