@sagat101 As pretentious as it sounds, there is a certain feeling that one gets from reading than one gets from watching that anime could never really encapsulate as of now.
@jslblaze
based on a penis being a defining organ of a male, the joke is that people who have big ones are very masculine, and people who have small ones that you can barely see lack masculinity, and aren't much different from women;
there is also this myth https://tvtropes.org/pmwiki/pmwiki.php/Main/BiggerIsBetterInBed
It's fine if you don't like the joke/myth because it has no bearing in real life (in fact too big ones could be legitimately painful for girls), but 18+ manga roll with it the myth very often
.