In the admin, set them to "Approved" > "No" and they won't show. https://www.socialengine.com/support/article/5210639/se-php-member-levels
That's how we do it here. :) We created a Banned member level and put them in it and then we put them at that setting. If you have your site set to require approval, that might cause you an issue but you can see what member level people are in before approving them. It's the only solution I could think of to hide them.