You cannot delete all your Facebook posts in one go since there is no ‘Delete Everything’ Button present. If you want to remove something, you manually must review the activities and then delete it. Still, if you want you can delete posts in batch with a simple browser extension for Chrome. It’s called Social Book Post Manager.
I believe, Facebook deliberately keeps a record of your activities for gathering data and using it to construct your personal Facebook profile. If you have certain apprehensions regarding this activity, try Social Book Post Manager extension for Chrome.
Social Book Post Manager for Chrome
1] Add the Social Book Post Manager extension to Chrome. After that, open your Facebook account and go to your Activity Log (visible as a down arrow adjacent to the question mark).
2] Instantly, you will be directed to a page that displays all the recent activity you have had on your Facebook profile including the posts you have liked, the friends you added and more.
3] Choosing to remain on this page, select a Filter you wish to delete from the left sidebar. For example, you can select the posts you are tagged in, other people’s post to your Timeline and more.
4] Click on Social Book Post Manager’s icon to open the extension. When done, it will display a list of filters that you can use to delete posts on Facebook.
5] You can specify the filters to configure the type of posts that should be removed from your Facebook account. There’s a ‘Prescan on Page’ option available which if checked will show the posts that will be deleted. If you find it ok, you can proceed to delete them permanently by clicking on the Confirmation button. Please note that the posts one deleted cannot be recovered.
6] Also remember, the ‘Prescan on page’ process isn’t so quick and can take an unusually long time to finish. It strictly depends on the number of posts involved. Facebook (TM) does not encourage users to easily remove posts. As such, they offer no shortcut to delete multiple posts in one go.
If the extension fails to work as desired, some other Chrome extension might be interfering with it. So, try removing/disabling other Chrome extensions temporarily. Then restart Chrome and check again if Social Book Post Manager works. Get it here!