The growing popularity of porn is to blame for the rise in rape culture. Porn culture has lead to growth of Rape culture. Porn dehumanises women as being just objects, women are no longer regarded as humans because porn regards women as objects to satisfy men's desires. Behaviours and attitudes must change for a decrease in rape culture. More guns will only lead to more violent crimes committed by men.
Woman where dehumanised long before porn was a big thing. The problem is when man also act that way towards women. Even worse when they get away with it because of their wealth and influence. Pretty much every for of media attributes to dehumanisation of women. Be it music, video games or movies it's not just porn. That's simply the most direct way to do so. But even without media people will dehumanise people (it also happens the other way around). As for your last point I agree that more guns means more violence. But also that counts for both sexes (wouldn't dare to assume a gender) although people with the chromosomes XY are naturally more violent and rapist.
Please excuse my (probally) poor grammar