Can′t log in on my website since I installed a "delete all comments" plugin.

I can not log in on my own administrator page.
The problem occurred since I installed a plugin, able to delete all (spam) comments at once.

My login page is full various amounts of text like these two examples:

Warning: Cannot modify header information – headers already sent by (output started at /var/www/tobiasvalentin.dk/public_html/wp-content/plugins/remove-all-comments/remove-all-comments.php:201) in /var/www/tobiasvalentin.dk/public_html/wp-login.php on line 444

Warning: Cannot modify header information – headers already sent by (output started at /var/www/tobiasvalentin.dk/public_html/wp-content/plugins/remove-all-comments/remove-all-comments.php:201) in /var/www/tobiasvalentin.dk/public_html/wp-includes/pluggable.php on line 957

I will end up in an asylum if this continues.