I recently had an issue similar to this come up. One of my GF's friends kept going on about how she'll only date black guys from now on because white guys can't cut it ect ect... My GF politely defended my good name and told her that I was probably more than her big studs had to offer. Her friend laughed, threw out a bunch of nonsense "facts" and claims of how big some of the guys were. While her friend was doing this, she reached under the table and began grabbing my cock thru my gym shorts and working it to hardness. After a minute or two of listening to her friends ramblings, my GF stopped her, grabbed her hand and put it on my cock making a pass up the length of it with her hand. Her friend went wide eyed, looked at my GF and said "OMG can I see it?" My GF asked "Why, you think its big?" to which she replied "It's huge! I wanna see it!" I was prepared to stand up and whip it out, but my GF being the awesomely cruel being she can be said "Sorry hunny, this belongs to me, you go play with your own 'big boys'."
I have to admit the whole scene was a bit surreal, I felt like I was watching a bad coming of age movie, but when it was all over I couldn't wipe the grin off my face and neither could my GF.
I love my GF.