He may be a great rock musician, I don't know (though someone who does not care for rock music will hardly consider it a great achievement). The problem is the poster which shows him smoking.
When you show such a poster to elementary school children, you are simply asking for trouble. If the teacher is such a great fan of Zeppelin, let him put up a poster of him, without showing him smoking. But to show a poster of a prominent personality smoking, to elementary school kids is nothing short of criminal.
Ok people.... first off, Led Zeppelin was not an individual, Led Zep was the name of a band, made up of Jimmy Page, Robert Plant, John Paul Jones and John Bonham..... kind of like how Pink Floyd wasn't the lead singer's name but the band's name. They never conjured up some tobacco smoking cowboy to represent their band, especially considering the band is from England, and they're a rock band, not country.
Secondly, the poster they showed has no relation to Led Zep, nor is it the poster in question of Led Zep... it was a tobacco ad the person in the link decided to use for their example of how bad they thought the Led Zep poster was, but they never actually showed the poster in question, which is where the confusion seems to lie in this debate.