How to Disable the BuddyPress Admin / Buddy Bar
If you want to disable the BuddyPress Admin Bar on every page throughout your site, add this to your wp-config.php file:
define( 'BP_DISABLE_ADMIN_BAR', true );
This is now the correct way to do it. It will actually work, whether you set it to true or false, as long as it’s defined. Read more about this issue here. However, if you’ve defined it as false in expectation of disabling it, based on how it was previously, there’s no need to change it, as it will still work either way.