I was rewatching The Lord of the Rings: The Two Towers. There is a scene where Saruman instigates 'humans' (men) saying the people of Rohan pushed them to the rocks or something of that manner. And the scene goes on with humans (men) running to attack Rohan. But, the village on the Rohan outskirts is sacked by Orcs. So what is happening here? Was it a movie mistake? Was it humans who turned into Orcs?
Yes, those were the men of Dunland (Dunlendings), whom Saruman riled up to attack Rohan.
There is a scene in the extended edition of The Two Towers where we see the Dunlendings' leader, Wulf, make a blood oath to Saruman.
Saruman is imitating Sauron, who recruits men to supplement his orc armies. Even though the Dunlendings don't appear to contribute much, they help show the extent that Saruman has become like Sauron.