There is no "ignore" for people. You can either just let them sit around in the "add people" section of the people album or add them all at once, then select them all and hide them. but hiding people will also exclude all photos of this person from the memories. If the offending people are in the background of a photo you want to use in memories you may not want to hide the person.
if you use brute force and delete the circle with the detected face from a photo, you will be left with white, empty faces thumbnails in the People album. I did this nevertheless and clicked the X on the faces circle to delete the detected face. Then I merged all white thumbnails into one big person album "delete" and are hoping for a bug fix in a later version to get rid of the white thumbnails. Repairing the Photos Library does not fix this.