Interesting question, and now, after reading the post again, I have so many thoughts running through my head, that I don't even know, where to start.

Since I lived in the US, I think I also gained an outside few on my own European culture and I automatically compare what you say to the situation here, particularly in Germany...

The convenient and easy thing is usually to focus and project outward, to fix blame or responsibility on someone else or something else. “They” should do something, we tell ourselves.

An attitude that actually annoys me, as I see it in so many areas, not only related to this particular subject. The politicians (and in consequence the industry) should do something to save the climate... they have to solve the problem with refuges... and so on... instead of people asking themselves, how they could contribute to a solution.

Unfortunately an attitude, that also leads to a movement towards right wing politics all over the world. A higher authority, (the famous strong (alpha) man) thinks for you, and takes the responsibly for your shortcomings away from you. Which I find particularly dangerous, when all that is tied to religion. But I guess, that's a whole different story.

To come back to your question, I wonder if that is really all there is.

historically unprecedented numbers of American gamma males to feel so overlooked, ignored, marginalized, disenfranchised and disrespected that their voices can only be heard via random acts of violence?

First, I agree, that there is historically unprecedented number of such men, who feel that way, but you have those here as well, if not everywhere. The feeling of being left behind just manifests itself differently. Here the weapon of choice might be cars and I wonder how the numbers compare between numbers of victims of shooting rampages and idiots killing people here in the streets with aggressive driving. In other cultures, these guys discriminate women or they live out their "problem" by joining groups, who terrorize the innocent and helpless... not necessarily for a good cause, that is really "good" after all...

I don't think we have more of these gamma males to feel so overlooked, ignored, marginalized, disenfranchised and disrespected you mention. Actually, I think (at least in the so called Western World) that group was much bigger only 100 years ago. So what is the difference?

Comparison and opportunity? In past times (even as recent, as my own childhood), when you belonged to the less privileged, it was just so. Everyone around you was the same and the possibilities to compare yourself to those who had more were limited. Plus it was more or less god given, into what social class you were born... Over the past decades however, it became at least theoretically possible to move up under the right conditions and the necessary effort. And right there you have it. If your social status is and remains low, either the conditions aren't right, and you seek somebody to blame for that (see above) or you didn't put in the proper effort and are looked down upon, because of that.

And now a third factor comes into play, which wasn't there in the past. Technology. Which multiplies the effect of "comparison" and at the same time makes it easier to be destructive on a large scale. One doesn't just see someone on the street, who has better clothes or other nicer things, one is bombarded with with it around the clock. At the same time its much easier now then past times (even if it was only from a financial perspective) to acquire the means to harm a lot of people, be it guns, cars or bombs.

Of course there is much more to it and I certainly don't have the answers to eliminate the problem. Actually, I think its unsolvable until everyone (on all sides) understands that "the human dignity is inviolable" and the value of life.