A way of weeding out certain words from your join form is throught the spam words array in config.php (the one in your main Enthusiast folder).

Put commas in between spam words and encapsulate in apostrophe’s, remember to escape any apostrophe’s within the spam word itself. No comma needed after the last spam word.

$spammywords        = array('viagra', 'cialis');

The above is the default but you can add as many words you want to not be allowed through.