BuddyPress.org

You can block them from being saved to the activity table (db)
https://wordpress.org/extend/plugins/buddypress-block-activity-stream-types/

(otherwise, posts on the forums about removing them from the activity loop array)

then if you need to block a certain blog_id (if on multisite)
etivite_bp_activity_block_denied_activity_type_check

this filter will pass a long additional data to check for – but you’ll need to dig into the code to figure that portion out.