This part of the article is not written in standard French: sentences have no end, are not really sentences as the verb is missing, and so on. No, there is no certitude of the interpretation proposed in "1", but it is not contradicted by anything. The interpretation in "2" is not at all likely.

Let’s quote most of the text where the extract is found (letters added).

• a Quand la discussion a été entamée à propos des signes religieux , Bouchard-Taylor, et ensuite de façon plus large à propos du fait religieux dans l’espace public, dans les institutions, ceux qui ont osé exprimer leur préférence d’un état laïc… Encore, en chœur, les mêmes, fidèles au poste…
  a’ « Les Québécois sont racistes », « les Québécois sont xénophobes », « les Québécois sont intolérants »…
  b À la suite de l’élection du Parti québécois, cette première tentative, chambranlante un peu, c’est vrai, de légiférer sur la laïcité de l’État; seconde grande discussion sur le sujet, transformée en foire d’empoigne, les gros canons, sur le pied de guerre…
  b’ « Les Québécois sont racistes », « les Québécois sont xénophobes », « les Québécois sont intolérants »…

What can be elicited from this text

On the whole the texte is a statement of circumstances (a, b) and the outcome, which is a reaction from some part of the population (a’, b’), always the same: "When this happens (a,b) that is the reply (a’, b’)". "a" is complex because it is made up of several elements not well connected.

First circumstance in "a"    Quand la discussion a été entamée à propos des signes religieux , Bouchard-Taylor, (after this results "a’")
Second circumstance in "a"     ensuite de façon plus large à propos du fait religieux dans l’espace public, dans les institutions, ceux qui ont osé exprimer leur préférence d’un état laïc… Encore, en chœur, les mêmes, fidèles au poste… (after this results "a’" again)
In this second part "ceux qui ont osé exprimer leur préférence d’un état laïc… Encore, en chœur, les mêmes, fidèles au poste" appears to be a parenthesis in parallel to that found in the first part (Bouchard-Taylor) — explained in my answer to a former question (answer); this is to say that if Bouchard and Taylor were at the root of the discussion re religious signs, those that dare voice their opinion were at the root of the larger discussion. However, although this seems very plausible, there can be no certitude. There are in the sentence no words allowing to claim that.

Moreover, there is no certitude of a parallel construction in the formulation of the second circumstance; what you expect and have to have so as to make a meaningful sentence is "et ensuite quand…" or an elliptical repetition of "Quand la discussion a été entamée", as your sharp suggestion brings to mind.

• Quand la discussion a été entamée à propos des signes religieux , Bouchard-Taylor, et ensuite de façon plus large quand la discussion a été entamée à propos du fait religieux dans l’espace public, dans les institutions, ceux qui ont osé exprimer leur préférence d’un état laïc… Encore, en chœur, les mêmes, fidèles au poste…

It does not make much sense to say that concerning (à propos) the religious fact the reaction was "The Quebeckers are racist", "The Quebeckers are xenophobic.", …

So, there is no definite connection between "Quand la discussion a été entamée à propos" and "à propos du fait".

"b" consists of just one circumstance.

Several parts of the text are not expressed, being certainly implicit to Quebecers.

Here is how I understand it as a native French, not being specially aware of the topic.

1. What is it about: Some people complain that Quebecers are racist, xenophobic, intolerant.

2. When did it start : When the discussion on religious signs was initiated (during the Bouchard-Tailor report times), and then later, when broader discussions on religious facts took place in the public space and in institutions (likely the parliament, regional and local places like municipalities).

3. Who were accused of being racist: those who dare to express their preference for a laïc (secular) state, i.e. for a strong separation of church and state.

4. Who accused them: As always, in unison, the usual ones (those who always complain, those who promote multi-culturalism).