My first experience with small penis humiliation was when I was about 14 or so. Its sort of a bizarre situation because I was still so young and innocent, chaste and virginal...but it left a deep impression on me, albeit with quite a bit of confusion as well.
I was over at my cousins home for a sleepover. My parents had some sort of weekend church retreat thing happening...which was a regular occurance, so sleepovers happened quite a bit. Anyhow another of our friends (same age as me, my cousin Karina is about a year younger) was spending the night as well, just to add to an all girl slumber party. So, as you do at that age, you get snacks, roll out sleeping bags on the floor, put on your baby doll nightie, and talk about boys and gossip about other girls.
Flash forward a bit and Janet (my friend) starting talking about kissing this guy, how he'd been groping her, grabbing her ass and so forth. So as somewhat of a late bloomer, I'd yet to have much dating experience (partly because of my parents being so religious, strict and controlling) so Karina and I were wide eyed, fascinated, excited and sort of scared.
As her story progressed, interrupted by us peppering questions to her, wanting details and graphic descriptions, (How did he smell, how did he kiss, was there French kissing?) she got to the part about rubbing his erection through his pants. Now, bear in mind that I knew nothing about nothing, but had always heard boys at school talking about "9 hard inches" and throbbing meat and all the usual innuendos, double entendress and dirty jokes, the assumption was that was true. So, apparently this guy had something more like a roll of pennies in his pants, when she grabbed it, she giggled and asked him "Is that all of it?" probably being genuninely confused, the same as I was when she described it to us. I don't recall all the other details, but I know it went something like, he got embarrassed, left in a pouting, harried, and hurried fashion and refused to lock eyes with her ever again....or at least the rest of that school year.
Without really understanding how or why, I got a little thrill out of it, hearing her story, knowing somehow that it was a sort of cruel thing to do, a bit of a sadistic thing, but the thought of it gave me a little "charge"...a little rush, and made me sort of excited.
Strange how something happens to you, so many years later that "sparks" those sorts of memories. :)