Prevent access to the "Friends" tab of a member profile, unless it's the user's own profile.

restrict-friends-tab-access.php

<?php
function bpcodex_remove_member_friends_nav_tab() {
    // Stop now if:
    // This isn't a user profile
    // This is the current user's profile
    // The user is a site admin
    if ( ! bp_is_user() || bp_is_my_profile() || is_super_admin() ) {
        return;
    }

    // Remove the "friends" item.
    bp_core_remove_nav_item( 'friends', 'members' );
}
add_action( 'bp_actions', 'bpcodex_remove_member_friends_nav_tab' );