Thanks for the reply Len.
It's definitely not my machine. I've experienced this on two different machines: one Macbook using FireFox and one Linux machine also running FireFox. When I was trying to troubleshoot what was going on, I ran connectivity tests using raw network sockets to their servers and they simply weren't responding (i.e. the web servers that they use for ads were not available at all).
Based on the feedback that I saw when I searched Google for other users having similar issues , they pretty consistently have issues and other users on other sites are noticing it as well:
tacticalrepublic.com slowing page loads - Google Search
Anyhow, I just thought you should know so that you could pass some feedback on to Tactical Republic.