Good points made so far, I think.
I would question the assumption that Airsoft users would be supportive of real guns.
After all, one of the main uses of Airsoft guns is to (pretend to) shoot and "kill" other people. While someone might find it fun to pretend to do that with other like-minded people, it may well enforce the idea that guns are inherently violent things, and turn them against real guns.
I quite like watching gangster films, and playing Grand Theft Auto. That doesn't mean I think such things are good when done for real.
As for why the UK is generally more anti gun (I can't speak for the rest of Europe), some points to consider (some have been mentioned already):
* Two World Wars have made people generally find militarism in all its forms distasteful. And unlike occupied Europe, the general population didn't need to engage in armed resistance against the Germans. (We did prepare for it quite extensively, with the Home Guard, but it was never required to actually fight).
* Generally low crime for a long period meant that there was little need[ for people to own defensive arms.
* Similarly, generally only the rural population has had much need for guns for work, and very few people hunt for food (and AFAIK no-one relies on hunting as a major source of food or income). (NB: in the UK, "hunting" usually means chasing deer/foxes etc with hounds; hunting using guns is normally referred to as "shooting").
* Much of the hunting community is aristocratic / upper-middle class. Meaning (possibly) a bit of bias in early firearm legislation against letting the proles have guns, followed by a backlash from the ordinary people when they got more power, who might have seen gun control as a way to get revenge on the aristocracy.
* "Entirely reasonable" registration and licensing of firearms, with no (obvious) intention of prohibition, that no-one would have any reason to object to...
* Followed a few decades later by "self defence" not being considered a "good reason" for owning a gun (in a country where there was never a great need to have a gun for self defence)...
* Meaning that when eventually a couple of nut-jobs went on shooting sprees, few people owned guns or saw any overwhelming need to have one, while the dangers posed by evil people with ready access to them were obvious.
(Take note America: we had a constitutional right to bear arms about a hundred years before you did, meaning our government and gun-control advocates have had a hundred years head start on yours. About a hundred years ago, our gun rights were still in a fairly similar position to where yours are now).
* Also an increasing culture of dependency on the government and "society" to take care of all your problems for you, and (commonly, not universally) a belief that the best solution to something bad happening is more laws. (PS: unlike in the US, the British police do have a duty to protect you, and there has been at least one case of a police force being sued (successfully, I think) for failing to take reasonable steps to prevent a murder that was obviously going to happen).
* Finally, a media (and media-consuming public) that always finds bad/sensational news more interesting than good (or no) news. And considers a psycho (especially in America) shooting 10 people more shocking that a psycho in some other country starting a fire that kills a hundred. (But then, that’s hardly a problem unique to Britain).
I’d say that’s a good summary of why the UK is generally hostile (or at best ambivalent) to guns.
As British/European hostility towards American attitudes to guns, I’d say take all the points I’ve just made, then add in:
* 10,000 plus homicides-with guns in the US (which without properly investigating all the issues surrounding crime, self-defence, the number of gun-owners who don’t murder people, crime rates in other gun-friendly countries, etc, certainly makes it look as if liberal gun laws lead to lots of shootings).
* A “kill ‘em all and let God sort ‘em out” kind of attitude displayed by some pro-gun contributors to gun-control debates (not as common on THR as some other forums I’ve visited, unless you’re talking about Zombies, but such sentiments do, unfortunately, seem to be more common here than when I first joined).