Hello ECHO-CHAMBER!!!
I just looked up and researched the term for the first time.
Yes, YOU ARE CORRECT. This forum is indeed an echo chamber. We are a collection of few hundred religious Jews, and while we may have different beliefs and views, we are more-than-fewer common denominators, some of them being very pro Israel belonging to Jews, and we all very against anti-Semitism (duh).
When someone posts here a ant-Semitic tweet or news article, the purpose isn't to "prove" anything to anyone (not to you or anyone else).
Why do we post it? I honestly don't know.. but even if you weren't on these forums, these posts would still be posted.
So I'm not sure why you are taking it as a "argument" (for lack of better word) and the need to play devils advocate all the time.
Of course we know that there other ways of looking at things, and while some of us might like the fun of it (trying to disprove you).. sometimes it just gets annoying.
So let's just all be on the same page.