It starts with objectively good advice like "work out and go to the gym to get a good body". Which is surprisingly on the downside in K-12 education. Then it drips in the narrative: "revenge training" to get fit not for your self-esteem but to make a bad breakup regret it, then into the "sigma male grindset", then if you do all this and you still aren't appealing it must be because of women. You worked hard, they don't get it or are too picky, or are looking for some famed gigachad with 8 packs and making 200k a year.
It's a slow drip into the pipeline.
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tangent: but in media male sexuality is much more suppressed too. You can show quite a bit of nudity in R rated films, but absolutely not a boner in any way 99% of the time. I don't think that changes much in society, food for thought.