I think the big difference lies in what the forums look like. 
While CGtalk is basically one big section where most people are somewhat anonymous, here at Renderosity people in one forum usually know each other well and know people using different apps in one or more of the other forums. 
Add to the fact that there are more beginners here(most of them are intimidated to post at CGtalk), and you get a completely different climate.

Although suckers do exist everywhere. I used to have my fair share of "This sucks" and similar comments in most places i´ve posted images, especially when i was using Bryce. I just didn´t pay them any attention unless they came with something constructive.

Any real artist know the value of using different tools for different purposes regardless of pricetag, so you should just treat snobbery like air and focus on the valuable comments. After all, those are the ones that really counts. 

Rudolf Herczog
Digital Artist
www.rochr.com