Hi, just came across your topic because I was looking for the same answer… And finally managed to find the way how to disable it.
Go to class-fire-init.php on line 178 and delete or comment:
$this -> font_selectors = array(
'titles' => implode(',' , apply_filters( 'tc-titles-font-selectors' , array('.site-title' , '.site-description', 'h1', 'h2', 'h3', '.tc-dropcap' ) ) ),
'body' => implode(',' , apply_filters( 'tc-body-font-selectors' , array('body' , '.navbar .nav>li>a') ) )
);