Ummmm,
bullshit.
This thing's got more red flags than a Chinese national parade. The link is to "Tabloid Prodigy," (a highly reputable website, I'm sure) who cite a post on (what can only charitably be described as a "sister" site) "Buzz Feed," which has all the appearances of a Maxim-Magazine-for-the-Web-only-run-by-even-more-depraved-pseudo-masculine-homophobes, which -- in their journalistic duty -- offer vague justification for the hack-job graph/chart plastered prominently at the lead of the article by kindly offering a link to "the British Medical Journal" ...homepage.
Only nothing in the most recent journal talks about penis size. Nothing in last month's issue either. Nothing in the last three years examines size and ethnicity, after both doing a search and manually scanning the archive. Only three articles since 2002 even mention penis size, and the only one that measured it against ethnicity (the 2002 publication) did so by measuring at birth, making the image spectacularly dubious.
"Buzz feed" even tags their posting with a 'dubious charts' label.
This kind of thing makes it to the boards every few weeks, in seems, and it always boils down to bullshit racist propaganda being spread, intentionally or ("simply") ignorantly, largely with the intent to incite the more rational and instigate a flame war or because the poster is just a gullible fool. (I guess they could be a mischievous bigot, but whatever)