Oh c'mon. I've been bypassing the firewalls at work for the last 9 years at least. I learned how when I worked at Cisco; the other employees showed me how when I first encountered a browser-related issue. Since then, I've noted several better methods, but I'm already setup for mine so there's no need to change.
Dilbert could subscribe to a web anonymizer site, for instance, that has lots of IP addresses that aren't filtered. His connection to it would be via https, so the traffic can't be easily viewed by those with only network access. Since I presume Dilbert knows enough to keep his system secured maybe put the cache in an encrypted file system or a USB jumpdrive), or browse from within a template-instantiated Virtual Machine that he can delete after each naughty use, or some other creative means (I have not listed ALL the ways - I suspect everyone does this a little differently), he should be able to surf with impugnity.
Wally very likely already does this, and as done it since firewalls became fashionable. He also knows how to eat food from the shared lunchroom fridge without getting caught.
Last October, a parent at the school where I work set up a website for a teacher to use in a lesson in November. I got to put through the request to unblock it. Lots of stalling. The lesson went on without the website. Tech Services unblocked it in January. And patted itself on the back for a job well done.
At least it didn't sabotage my career, but it sure didn't help the kids' education.
If there is a Hell, people like this who abuse power over others will spend eternity buried up to their chests in the mud of a Congolese blood-diamond mine, whipped constantly for every groan of misery. (Dreaming is all we can do, since real life never tends to punish douchebags like this sufficiently; only in rare occurrences do corporate (or military) bullies get the come-uppance they deserve.)