Hunting is the issue, not gun ownership (not much of a contentious issue so far). There's a strong culture of hunting in rural areas, a right that developed after the French revolution: until then, hunting was reserved to the nobility and any commoner caught poaching, even during the worst famines, was hanged. So hunting is also seen as a conquest of republican egalitarianism.

Unlike other European countries like Britain or Germany, France remained a largely agricultural country until WW II: in 1939, the majority of the population still lived in rural areas rather than in the cities. All this changed radically during the three decades of growth into the first oil shock: the rural areas are becoming increasingly empty and even small and medium towns are struggling to keep population (and jobs) to the benefit of the big conurbations like Paris, Lyon, Marseille, Lille, Toulouse, Bordeaux, etc...

Farmers themselves have become an endangered species, living more and more out the CAP subsidies.

In parallel, since the 1970's, more and more legislation (some of it pushed by the European Parliament) was introduced to protect wild animals, including a lot of traditional game and traditional hunting methods, like "chasse à la palombe" (Common Wood Pigeon) in the South West. The growing restrictions on hunting, coupled with an increase of suburbia encroaching onto what was previously farming land has created a strong resentment against all these bobos, urban, hippies, pinko/commies/environmentalists "who want to take away our legitimate right to hunt".

This is why there has been a party called CNPT ("Hunting, Fishing, Nature, Tradition") who presented candidates during most of the election cycles since 1989, including presidential elections.
This is a conservative movement of the reactionary kind, surfing on the fears and travails of the rural world. It is aligned to Sarkozy's UMP since 2009.

It would be wrong to paint all rural people with a reactionary brush anyway: several small farmers movements (ex: José Bové) are supporting progressive policies, including on environmental issues (afew who's living in a mostly rural place, could expand on this).