Defined as: an insular communication space where everyone agrees with a certain piece(s) of an ideology and no contrary input is allowed (edited version of this definition)
I am not convinced that jesviro or javiro are clear in Esperanto, but jesulo and jesemulo seem to have at least a small amount of traction - in one or two user-edited dictionaries. This calls to mind the term jesemulejo.
- Mi pensis ke mi bone esploris la aferojn kaj petis opiniojn de aliaj, sed Esperanto Stack Exchange fariĝis malsana jesemulejo.
My initial guess would be Unuecidea Ĉambro or Ĉambro de Unueca Ideo, but these are only to convey the idea if someone hadn't hear the term before.
A direct translation could be Eĥĉambro" (Eĥa-Ĉambro) or "Jesvira Ĉambro", as in a room filled with Yes Men. You could also use Javira Ĉambro, which I like more since the imagery is better and sounds better (A room full of men going "INDEED!" to someone)
Is there anything wrong with saying it the way you just did?
- "insular communication space where everyone agrees with a certain piece of an ideology and no contrary input is allowed"
"Mi kredis ke mi profunde pripensis tiajn aferon, sed nun, de la alia flanko de kredo, mi vidas ke mi komunikis nur kun personoj kiuj jam trovis la samajn konkludojn kaj mi neniam aŭdis novajn ideojn."
It seems a little bit too much to expect to find a metaphor which will be immediately clear to people from all different cultures, so it's probably good to spell it out clearly.
I play around with the the idea of calling it samideanejo (a place where people with the same idea gather) but the problem is that samideano has the specific meaning "Esperantist" in Esperanto.
So perhaps samismanejo (where adherents of the same ideology meet) is a trafa vorto.
EDIT: I think the word can be shortened to samismejo (leaving the -an- out, "place of same ideology").