Need help pulling post_type and tag_ID

I have worked out a function that will show me authors of a certain category, specifically based on post_type. This is fantastic, however I have two post_types that each have their own categories or tag_IDs. For example, I have two taxonomies: Fruit and Vegetable (or post_types). This code works to pull up only the authors that post in Fruit:

<?php
            $args = array(
		'post_type' => array('fruit'),
		'exclude'         => '1,2',
            	'optioncount'	=> true);
            get_authors_by_post_type( $args );
?>

This is what I put in my functions.php to get this to work:

function get_authors_by_post_type($args){
	global $wpdb;

	$defaults = array(
		'post_type'=>'post',
		'exclude'=>'',
		'exclude_admin' => true,
		'echo' => true,
		'optioncount' => false
	);

	$r = wp_parse_args( $args, $defaults );
	extract( $r, EXTR_SKIP );

	$post_type = (!is_array($post_type)) ? array($post_type) : $post_type;
	foreach($post_type as $key=>$value) {
		$post_type[$key]="'$value'";
	}
	$post_type = implode(',',$post_type);
	$exclude = ($exclude) ? "AND p.post_author NOT IN ($exclude)" : '';
	$sql = $wpdb->prepare("SELECT u.ID, p.post_author, COUNT(p.ID) as count, u.display_name
FROM $wpdb->posts p
JOIN $wpdb->users u ON p.post_author = u.ID
WHERE p.post_type IN ($post_type) AND p.post_status='publish' $exclude GROUP BY p.post_author ORDER BY u.user_registered");
	$authors = $wpdb->get_results($sql);

	$return = '<ul>';
	foreach($authors as $author){
		$posts = $author->count;
		$author = get_userdata( $author->post_author );
		$name = $author->display_name;

		if ( $author->first_name != '' && $author->last_name != '' ) {
			$name = "$author->first_name $author->last_name";
		}

		$link = '<a href="' . get_author_posts_url($author->ID, $author->user_nicename) . '" title="' . esc_attr( sprintf(__("Posts by %s"), $author->display_name) ) . '">' . $name . '</a>';

		if ( $optioncount ) {
			$link .= '&nbsp;<span>('. $posts . ')</span>';
		}

		if (is_author($author->ID)) {
			$return .= '<li class="current">'.$link.'</li>';
		} else {
			$return .= '<li>'.$link.'</li>';
		}
	}
	$return .= '</ul>';

	if ( ! $echo )
		return $return;
	echo $return;
}

Awesome. Now in Fruit, I have Oranges, Bananas and Apples. However if I plug in what appears to be their tag_ID or slug I cannot get anything to show up. Any thoughts on how I would pull this information? Any help would be MUCH appreciated as I am really determined to make this work.