Make a BuddyPress profile field un-editable. Requires the ID of the profile field(s)

buddypress_field_uneditable.php

<?php

function cp_makeProfileFieldUneditable( $retval ) {	
	if( is_user_logged_in()  && bp_is_profile_edit() ) {
        $retval['exclude_fields'] = '1';	// field id's
	} 
	return $retval;
}
add_filter( 'bp_after_has_profile_parse_args', 'cp_makeProfileFieldUneditable' );