Tell SEO bots to not index Event Espresso taxonomy pages.

robots.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file
function ee_no_index_tagseo_meta() {
  if (is_tax('espresso_event_categories') ) {
	?>
	<meta name="robots" content="noindex tony">
	<?php
  }
}
add_action( 'wp_head', 'ee_no_index_tagseo_meta', 9 );