If you improperly equate these two instances, they were probably right.
A fossil is a snap shot in time of a particular creature as it's body was covered in mud or silt; that being the case, one can't conclude based on a single case, if it was featherless because if had no feathers, or if it moulted before dying, or scavangers devoured the feathers after death but before the body was covered up with silt. [Caveat: if the fossil is sufficient quality that it shows skin details, I MAY be possible to deduce that the creature NEVER had feathers; just as one can tell between the skin of plucked chicken and the skin of a human, which one had feathers and which didn't.]
A foot print, on the other hand, is a foot print indicating a particular creature stepped in a particular place at some point in time. If you have evidence that based solely on the footprint and no other information, some scientist concluded the creature had to be vegetarian, feel free to post it.
Based solely on the footprints they determined that the dinosaur was a meat-eater.
http://www.freerepublic.com/focus/f-news/1504547/posts