I don't know what's going on with that post, but having a penis that is significantly larger than average can cause a lot of problems for your sex life. The vast majority of people with vaginas have average vaginas that more or less match up with average penises. If your penis is too big it can be uncomfortable or painful for your partner, or you might just not be able to get it in at all.

Combined with the social expectation that bigger = better for penis size a good number of people end up depressed, alienated from their own body, and convinced that they'll never be able to have successful romantic or sexual relationships. This is an issue that's difficult for people to talk about because for the most part it's uncritically assumed that having a large penis is more desirable, so you're liable to be mocked or shamed if you try to confide in someone.