Why did Little John have a modern day haircut?

Seriously? Out of all the things that were out of place in this movie, the only one that stuck out to you was John's haircut?

They hardly ever get the haircuts right in period movies, mostly because making them accurate would risk making people that we are supposed to root for unappealing or downright ridiculous. It's a shame they didn't go with real early 13th century fashion for Marian, though (or even late 12th century: she wasn't at court, she could have been a little behind in terms of fashion). There were some truly beautiful things at the time.

"Occasionally I'm callous and strange."

Actually it was totally in keeping in the film, because virtually nobody had a medieval haircut. In fact Little John, Will Scarlett, Alan A'Dale and Robin himself had such similar modern haircuts that I truly can't see how you could pick out one as 'out of place'.

John's haircut never really bothered me. On that note, there was a guy with spiky hair in 'Gladiator'.