I doubt you'll convince anyone to turn OFF their firewall. However, I'm firewalled and have had many users d/l from me successfully. It's more a matter of understanding TCP/IP and firewalling technology. That's a serious problem.

There are plenty of ppl out there using firewalls who don't really understand what they're doing. This could actually be a bigger security risk than not using a firewall. If you don't know how your firewall works, then you don't know how to secure it. If you don't know how to secure your firewall, then you're prolly just lulling yourself into a false sense of security.

Whether you're running Linux or not, i suggest going to:

http://www.grennan.com/Firewall-HOWTO.html

That documentation is for Linux firewall software, however if you don't understand the basics, it's also a pretty good resource for those just starting to learn about the TCP/IP protocols and what your firewall (any firewall) is doing.