If Statement – if current post is a child of a post with a taxonomy

This will get all custom post ctp_slug assigned to any term of home-theater taxonomy and return array with posts ID. post__in parameter will limit results to only post with given ID.

$args=[
    'post_type' => 'ctp_slug',
    'posts_per_page' => -1,
    'offset' => 0,
    'fields' => 'ids',
    'tax_query' => [
        [
            'taxonomy' => 'home-theater',
            'operator' => 'EXISTS',
        ]
    ],
    'post__in' => [parent_ID],
];
$result = get_posts($args);

Edit #1

function get_sidebar_ads_above_tabs_conditional()
{
    global $post;
    $parent = $post->post_parent;
    $parent_has_tax = (!empty($parent) 
        && has_term('home-theater', 'projector_types', $parent))

    $returnValue="<div style="margin-top: 20px;">";
    if ($parent_has_tax)
    {
        $returnValue .= '<div>Banner Ad 1</div>';
    } else
    {
        $returnValue .= '<div>Banner Ad 1</div>';
    } $returnValue .= '</div>';
    return $returnValue;
}