BuddyPress.org

Search the plugin files for something that looks like:
add_action( 'bp_nav_items' .....
‘bp_nav_items’ being the operative code here.

If you find something, let’s say
add_action( 'bp_nav_items', 'add_discussion_tab_function' );
copy that line, change ‘add_action’ to ‘remove_action’, and put it in the functions.php file of your theme. That should make sure that the tabs don’t appear.