It annoys me that people can just put me in groups on Facebook. I hope Facebook changes this soon. Also, it isn’t obvious how to get out of the groups. This annoys me too.
Here’s how to leave a group.
First, click on “See All” underneath groups. A list of all groups will show up. Look for the X to the right after the name of the group. It will ask you if you want to leave the group. Click yes.