If someone has leftover (non-vegan) food that they are about to throw in the garbage, freegans would generally eat that food, because doing so wouldn't cause any additional animal suffering. However, instead of eating it themselves, I think it would be better to give that meal to an omnivore instead (one who does want it). By giving the meal to an omnivore, you have delayed their next visit to the grocery store. You have lowered the number of pieces of meat they will buy in their life by one. Even if none of your friends or coworkers want it, you could probably find a homeless person who does. Seen in this light, you really have no excuse for eating that piece of meat yourself, because it could still be used to prevent more animals from being killed.