block activity type buddypress or bbpress

/*  paste in the functions.php of your active theme */

function wudaa_activivity_dont_save( $activity_object ) {
	// friendship_created is fired when a member accepts a friend request
	// joined_group is fired when a member joins a group.
	$exclude = array( 'friendship_created', 'joined_group');

	// if the activity type is empty, it stops BuddyPress BP_Activity_Activity::save() function
	if( in_array( $activity_object->type, $exclude ) )
		$activity_object->type = false;

}

add_action('bp_activity_before_save', 'wudaa_activivity_dont_save', 10, 1 );





// Filter bbPress from updating activity stream
function mulito_activity_dont_save( $activity_object ) {
$exclude = array( 'bbp_topic_create', 'bbp_reply_create');

// if the activity type is empty, it stops BuddyPress BP_Activity_Activity::save() function
if( in_array( $activity_object->type, $exclude ) )
$activity_object->type = false;

}

add_action('bp_activity_before_save', 'mulito_activity_dont_save', 10, 1 );