The whole thing comes from two premises
1) Fielded in this post - the Republicans deliberately moved the primary up to disqualify the Democratic candidate, so that they were left in a weakened position, and they could steal the 2008 race as they did in 2000 and '04.
2) Florida moved the primary up because they wanted more influence in the national debate, and more say in picking who would be the nominee.
The Democratic Party leadership (Howard Dean, and his subordinates) did not like this. The order of the primaries was supposed to be unchangeable (New Hampshire, and I think Iowa, have it written into their constitutions that they're first. If someone moved the primary ahead of NH, they'd have to reschedule it even earlier to comply with their own law)
Now when the DNC said that the two states couldn't move their primaries; it would have been sporting to remove your name from what would be an illegal or invalid primary (as all by Hillary did). Not knowing that this would be a slugfest to the end, they presumed that faced with the fiat by party headquarters, the 2 states would reschedule like good little minions..