It's quite a good idea for a thread, although it will probably be extremely controversial and some people may be offended by it. I would be more specific, as well, such as saying which league (and moving this to 'English Football') and maybe getting some statistics (and also giving a reason) for your suggestion.
I personally would agree with you, in saying Wigan have the worst fans, but it is general (some Wigan fans are loyal and good, but some are quite poor). However, it may be because they don't have as many fans as some of the 'big' teams (such as Manchester United, Manchester City, Liverpool and Arsenal).
I think what highlights my statements is the fact that mostly (especially when I see it on Match of the Day) they do not fill their stadium up and there are many empty seats. This is not me being purposely biased, by the way, as I am an Arsenal fan. The best fans in the league, I think, have got to be Newcastle fans in their huge numbers. The Toon follow N'Castle through thick and thin and as a local club (many of them have gone to Saint James' Park).