My reaction was pure shock, but there's a story as to why. I grew up going to gyms, pools, etc. where there were really no black people. That's just the way it was. Fortunately, I also grew up with the right parents...so, while our uncles and cousins used the "n" word frequently, we were taught right, in other words differently.
One of my summer jobs during college (I was 20 at the time) was in the steel mills of South Chicago...in the "harbor area." As a college student/summer worker, I was rotated around a lot - both location and shift. One week I worked in the blast furnace area...pretty tough stuff. One of the guys on my shift that week was a young black man (maybe in his early 20's), whom I really didn't know and wouldn't recognize today. He was very tall (6'4" maybe) and lanky - sort of like a Randy Moss type. There was a locker room available for the shift workers because the blast furnace was such a rough place to work. It allowed them to shower, clean up, etc. I remember walking in there by happenstance to use the toilet and this guy was standing, just showered, near his locker...maybe 15 feet away. Between his legs (yeah...just like everyone else - gay or hetero...I "peeked") was something that looked to me like a baby python. It must have been 7-8" unfurled, uncircumcised and very thick. Given the fact that that was my first encounter with a black cock, it was easy for me to buy into the myth until I became a bit more reasoned as my life progressed. But, I will admit, that deep down inside of me - where my ability to reason is hard to find - I still believe that black men generally have very large cocks. Not rational, not racist either. Just the effect of that moment on me.
