The first one is a bit more personal, as my parents repeatedly ask me 'when I will grow out of video games'. Fair enough, no retort can tackle that statement ('you don't get it/it's not for kids' always falls on deaf ears and is a faux pas instead of an ironclad response). In terms of being anti-social...well, my own upbringing has led me to rely only on myself, so I'm very introverted. I need my alone time, and when people interrupt this, I can get aggressive(though it isn't limited to games, I just want to shut the outside world every now and again, as it helps me think and relax). In terms of social situations, others have told me that I'm relatively easy to talk to, and I enjoy outings with friends. I can operate as an introvert or an extrovert and still have fun, it's just that if I want to relax and recuperate, I go into introvert mode. But all people need is a few examples of introversion and they see that as chronic behaviour. Also apparently, 'online interactions with online friends' doesn't count. Even though they've proved to be as good friends to me as my real life buddies, if not better in some regards, because I can talk to people online about anything without worrying about how it may reflect on me as a person.
Games aren't there for cheap thrills at their core. They can certainly be about pure fun, but instant gratification isn't a universal law applied to all games. Spec Ops The Line is not even in the same universe as the word 'fun', and The Witcher 2 serves as an anthropological journey into eastern european feudalism and political scepticism. Neither of those games are outright fun, and they do require considerable thought to enjoy/immerse.
As for being a loser...well that's your own definition. More often than not, that word is applied pejoratively against people that the person in question is angry at for not enjoying life the way they expect everyone to enjoy it. It also often reflects a level of arrogance, in assuming that everyone is like them.
Being a 'fat neckbeard' isn't exclusive to games; gaming includes a vast swathe of people of all different shapes and sizes. There is no one stereotype. This is again, applied to insult and diminish gaming and the culture surrounding it. I don't see myself as particularly unfit. I am reasonably physically capable, and I just need more work to reach an optimal health standard, though by no means anything excessive. I also wash often, so I'm not really sure if that assumption holds any water as of late.
'Children's past-time' reflects an echo chamber mentality. I'd dare you to show me one child who can play Shogun 2 or even Civilization V. Those games are complex as all hell, and the ratio of 'universally simple' to 'ungodly complex' games is evening out due to the resurgence of 4X and space sims that the PC side of things is getting.
'Violence and psychopathy' is just false. It reflects a greater problem of disassociation and refusal to accept in society. Games/violent media are often blamed because the accusers in question cannot believe that someone could act in such a dangerous manner. It feeds into the earlier idea of 'everyone is like me'(which is probably some evolutionary trait, but the point of modern society is to transcend evolutionary mentalities). Accusers often assume that everyone is normal, and that some outside influence must have manipulated a person into committing a violent crime. Games are an easy target, as the community tends to keep to itself and doesn't hold as much direct sway as movies do(saying that a violent movie caused a murder is more difficult). Games do not cause violent behaviour. Also violence is everywhere. Violence is a method through which to explore the human condition, and if a game is rated 18+ then it means that it's not for kids. It means that its allowed to explore taboo or explicit subject matter, as it has a specific, legally-enforced barrier to entry. Violence is usually used in relation to kids playing material beyond their age, but this is more often due to lazy/negligent parenting than anything else, but again, 'relinquishing responsibility' and 'everyone is like me' is at work.
I have been aggressive, and I still have occasional outbursts, but I've never harmed a single person in doing so. I shout, yes, but I see that as a more acceptable substitute over fighting or property damage. I've gotten angry over games or when someone says that 'games are controlling me', but these people usually see my outrage as confirmation of their own behaviour, because of again, the mentality that 'everybody is like me'. I mean, why should someone calling me 'a junkie' or 'a child' or 'mentally ill' ever make me upset(?). As for gaming addiction, more often than not, it's used in labelling terms by outsiders. People who genuinely give up their real life for the sake of a virtual one are far more rare than people who might turn down a social opportunity for the sake of playing a game. Games are not inherently addictive. You can cry to me about how they stimulate the release of adrenaline, but many other activities do the same thing without being branded as addictive. Simply put, the act of gaming itself does not directly create or condition the brain towards a biological need to game. This is again, often used to disassociate gamers as being 'not normal', and that the hobby is 'undesirable', by outsiders. I always have control over whether or not I want to play or not. If there is work that needs to be done, I'll get onto it. If it's a school night, I'll go to sleep at a reasonable time. But if I just got a game, or if I have an abundance of free time in which to play a game, I don't understand why it's seen as 'bad' if I want to game for a few hours. I don't relinquish control any more than people who go on movie marathons.
For the current stuff, there's no way to prove that you're not sexist without sounding superficial. "Why yes, I do have female friends! Here's one! Look! Look! See? I'm not sexist!". Personally, I identify myself as not sexist. I believe in equality for all, and I never use a social label against a person(be it, gender/sexuality/etc.) if I am angry at them. I believe I serve as enough of an example to prove an exception to the rule. I can carry a conversation with a girl that I may find attractive without being weirdly inappropriate or 'to get sex'. I interact with a person because I want to interact with them, not because I want something out of them.