If a judge had rejected this warrant on the basis of that paragraph, the police could have just removed it and we and the judge wouldn't have anything to complain about.
The grounds for the seizure were plenty strong - the email traces and network authentication would be enough to get any laptop involved in a crime seized.
And as for people claiming it wasn't a crime - there is no possible way that there was no malicious intent in sending a personal-attack email anonymously to a large group of people. (edit)In this case(/edit), the free-speech argument kind of loses its luster when you send something without your name attached.