Buy-in level.
...
You literally need just a pen and paper to get started in this hobby. You don't even need to buy a gamebook -- you can borrow a friend's or even spontaneously come up with a primitive form of RPG yourself. You don't even need to GM.
Even computer games require you have a PC, a games console or a handheld device AND THEN have a copy of the game itself to play. It is very unlikely -- outside of your teenage/undergrad years -- you will know someone you can just borrow expensive kit like that. You cannot spontaneously come up with your own computer game -- that requires a talent called "programming" and that's just cut off 70% of humanity already from the jump.
Archery: you need to pay to be a member of an archery association, plus regular dues to a club you've joined so you can shoot at their range and use their equipment (+ your own personal gear expenses)
Sailing: you need to at least pay a time-share on a vessel, you need to have training and a license to sail, you need to have a full day free to really get anything out of it
Foodie: you need to have the disposable income to afford to eat-out regularly (w/ everything that includes) at nice places and to be able to take the all-too common financial risk that a restaurant or hole-in-the-wall might suck.
And on and on and on.
...
The vast majority of hobbies require decent disposable income and/or some level of skill to do them at a level where you're getting anything out of them.
This means we've already filtered for a certain caliber of people. If you have even half-decent disposable income AND you're paying rent and bills, you're probably going to be at least semi-competent socially. And if you're a snooker cue, it's likely going to be in an endearing or charming way.
In my experience, in the many online and offline games I've run, at least half the table is filled with people who are shift workers, on contract or are students. The other half is usually like myself (NB: I'm in my twenties): white-collared, salaried young professionals or those who run their own companies (either straight successful or getting there).
When the former group come to play, a lot of them are there for power fantasies and vicarious gaming. If they're players, they come to get themselves validated; GMs, they're there to get control over something in their lives. The latter group -- we don't need that because we're already leveling up in real-life. And that's a 100% real.
So that's where, most of the time, you get jerk RPGers in general, not just GMs (because in my experience, players are usually the problem, not GMs).
That's not what I asked; you're begging the question.
You've explained why you think there are more jerks in our hobby than others. My question was: are there more jerks in our hobby than others? I'm not sold on the premise that there are. Without establishing that the premise is true, explanations for the premise are rather pointless.