It has nothing to do with double standards, it has to do with the fact that these bots are terribly difficult to trace to their true owners. If you were to serve a search warrant on the ip address one of these messages came from, you are not likely to find yourself in the server farm of a nefarious porn empire. You'd find yourself at some common person's household; a person who has no clue his computer is infected with malicious software that is spamming thousands of people and is simply flustered as to why his computer is so slow lately. Most of these bots operate from the computers of normal unsuspecting people, businesses, and even government agencies with no idea their system is infected and being remotely controlled to send out spam.

Authorities do try to go after the people behind these bot networks and put them in jail. A few people were just arrested in Spain the other day and it's been all over the major news networks.