This "explanation" is sometimes offered to me as a reasonable justification for why some young men are oblivious to their privilege, are acting aggressively, and/or are being rude to women.
Once, when I was guest blogging at a conservative site, I gently took issue with one "fresh from undergrad" young man's, ahem, problematic behavior, and an older man associated with the site privately emailed me to request that I give the young guy a break because he's just a young guy, visibly upset by the encounter, and so forth. (Men acting problematically often have very delicate feelings, you see, even as they mock feminists for being over-sensitive. Hence, the dance we often have to play with the word "problematic.")
Another time, I was on a project with a young guy, new to working, who was hyper-defensive about even the minutest of critiques and suggestions to his work. He strutted into the workplace both assuming he had lots to teach everyone else, especially the women, and believed that much of the work in his job description was "beneath" him. He was the Big Picture Guy, or so he thought.
Every conversation with him was a battle in which his sole objective was to "win" everyone over to his viewpoint. He had no capacity to understand that maybe, just maybe, he didn't automatically warrant an immediate CEO position. He didn't get why people didn't just do what he said, just because it was him saying the things.
"Well, he's young," some people would say.
But, the thing is, I know many young people, men and women alike, and not all of them are assholes. Many of them are kind, aware, and humble. Many of them believe they have things to learn from other people - about work, about privilege, about other people's life experiences.
I do not deem "Well, he's young" to be a sufficient reason to explain away a young guy's assholery. When I hear it, I hear a phrase that enables young men to their entitlement to be fonts of unexamined privilege and illusory superiority.