Questions concerning heterodox schools of thought should be perfectly acceptable. If we are to assume that economics is an objective discipline with methodologies driven towards positive instead of normative truths, then heterodox school questions should be fine. However, I do think someone asking a heterodox school question should be self aware. They should understand that the assumptions that they're making (or the assumptions that they refuse to make) contradict or conflict in some way with mainstream economics.
I believe the way we word questions can radically change the tone in which the community can answer it. Instead of asking, "Why are Keynesians so dumb with their obsession with aggregates?" one can instead ask, "What are the responses to criticisms towards aggregate analysis?" One should not ask, "How can Austrians actually believe that there are no market failures?" A better and more formal question would be, "What is the response to the 'Negative externalities are the results of unresolved property rights' critique?" Remember, economics should be a positive discipline. Every school that treats economics in that sense should be open to discussion. And honestly, if we look at the differences between the different schools it all really boils down to methodology and assumptions. Neoclassicals make more assumptions about rationality than, say, the Austrians do. But that doesn't mean we can't ask about neoclassical rationality. It's a concept, developed and defended by very smart and very well educated people. We should be able to answer a Neoclassical question by stating, "Given X, Y, and Z here is my answer. However, I do not believe X, Y, and Z can be assumed so easily."
For example, I think cost curves are fallacious. If you take a microeconomics course, you learn about subjective value; and then, these objective cost curves appear in the following chapter. That doesn't mean I can't answer the question with cost curve analysis. The goal of an answer isn't to show what's right or wrong on any holistic level. The point of answering a question is to answer the question at hand. By having guidelines on good questions and good answers, we can allow for a huge breed of thought to exist without running into errors of meta-arguing.