Hmm... Thanks for the advice. It's difficult for me to defend my Founder because inevitably, I send him out to "FIGHT EVIL" and he dies on site. Only once have I had a raid on my turf, and that was in the game with the hackers. Fortunately, I had moved them to another building, but they were not defended so they all died. I guess what I'd really like help with is, how on earth can you defend yourself? My founder always dies before getting a weapon skill up to any appreciable level... 
Remember that it's better to be arrested then dead. A dead liberal is gone forever. If your arrested you might get off (especially if your working the system, sleeper judge and attorney is great, sleeper judge and ace attorney are awesome) and even if your sentenced to death or many years, you can break them out of prison. I regularly let my actively criminal liberals get arrest so they have a clean slate and I can avoid cop sieges.
Merc and CIA sieges have to be fought off however, so make sure you have a lot of liberals on site (they all get to shoot during a siege, not just six) and lots of good guns. Smg's and shotguns are good for liberals without much skill. Traps are excellent. Hide deep in your fortress until there's a bunch of bad guys who've stumbled into traps and you can tear them to pieces when they can barely defend themselves.
Body armor is good for the six that get shot at. If you have lots of cash (which is easy if you're spending lots of time laying low in between elections by just fundraising) you can have a turned vigilante or merc (non conservative mercs can also be recruited IIRC) train all the liberals at a sight but make sure you have lots of cash because this is very expensive. This isn't necessary but can help.