My favourite superhero is Superman. I've also got a soft spot for Spiderman. I started reading Superman to see how strong he was but found I really liked the stories being told.
Thanks for being so open minded, i've met so many dbz fanboys who are so closed minded they would never accept the fact that goku could lose period.
I think its that they can barely comprehend that Goku could be beaten. I've felt the same way in the past. I think it's because in the anime and the manga a lot of time is spent reinforcing how powerful the characters are. Not by feats like in comics but by hyperbole coming from the characters themselves.
Think about how much of the show is spent on characters gasping at the jumps in power or characters screaming how strong they are. It's why most DBZ fans reject the evidence that the Z fighters aren't physical powerhouses compared to comic book heroes. It doesn't fit their view of Goku, which isn't the Goku shown in the fiction.