Even though you can’t stop people from adding you to groups, you can remove yourself from the group. You’ll know that you were added to a group because you’ll get a notification that “so and so” added you. Also you’ll probably start to receive notifications of new posts in the group. So here’s what you can do to remove yourself.
Go to the group that you want to leave. If you’re not sure which one it is, you can see all of your groups by clicking on the “more” link next to Groups in the left column of Facebook.
Once you’re in the group, click on the gear icon – under the cover image and to the far right. From the menu, select “Leave Group.”
A confirmation message will appear, asking you if you’re sure that you want to leave the group. You can also choose to prevent other members from adding you back to the group.
If you want to report the group for any reason (harassment, explicit content, spam, scams, hate speech, violence), click on the “Report Group” link at the bottom of the confirmation message. Otherwise, just click the “Leave Group” button. That’s it. You’ll no longer be a member of that group and you won’t be re-added. Now you can breath a big sigh of relief!