I'm not surprised by that either. I was reading about the history of the band somewhere online and it said that Jimmy's initial vision for Zep was to "go to America and play heavy music," or something to that effect. He knew there was a HUGE market for that in the States. They were the perfect band at the perfect time for that market.
A great rock song with one of the most memorable licks in the history of rock. I love playing that lick (and Whole Lotta Love) on my Les Paul. I think people are taking the song too seriously here, trying to analyze it through a politically correct lens. Lighten up, people! It's a fun, tongue-in-cheek rock song.