How to log out without confirmation ‘Do you really want to log out?”?

This happens because you are missing the neccessary nonce in the URL, which is being checked in wp-login.php

case 'logout' :
    check_admin_referer('log-out');
    ...

Use wp_logout_url in order to retreive the URL including the nonce. If you want to redirect to a custom URL, simply pass it as an argument.

<a href="https://wordpress.stackexchange.com/questions/67336/<?php echo wp_logout_url("/redirect/url/goes/here') ?>">Log out</a>

You could also use wp_loginout which generates the link for you including translation:

echo wp_loginout('/redirect/url/goes/here')