I don't see how preferring big dicks in porn is any different than preferring heavy weight boxing or professional athletics over amateur athletics. I don't watch the WNBA because I prefer seeing top tier competition, be it the NCAA or NBA. I wouldn't watch Canadian football over the NFL. Likewise, I would rather see a top BBC performer over some limp dick amateur.
That's because you like dick and find big penises aesthetically pleasing.

Don't worry, I'm the same way with dick. Big dick is just nice to look at and looks hot. It's like breasts. Big breasts are nice to look at, but for practical and reasonable circumstances, they aren't a requirement when hooking up a lady. The same thing is true for dick and men. Large cocks can be hot, but you don't want to go down with an extremely large one for practical purposes.
It is okay, I understand how you feel.