This is a very quick and dirty way to remove those feeds –
add_action( 'bp_init', 'disable_bp_activity_feeds' );
function disable_bp_activity_feeds() {
remove_action( 'bp_actions', 'bp_activity_action_sitewide_feed' );
remove_action( 'bp_actions', 'bp_activity_action_personal_feed' );
remove_action( 'bp_actions', 'bp_activity_action_friends_feed' );
remove_action( 'bp_actions', 'bp_activity_action_my_groups_feed' );
remove_action( 'bp_actions', 'bp_activity_action_mentions_feed' );
remove_action( 'bp_actions', 'bp_activity_action_favorites_feed' );
}