A prime example for my question would be the Communist Manifesto (where I believe Marx would be considered a philosopher) and Mein Kampf (where I do not believe Hitler to be considered a philosopher). Mein Kampf criticized Marxism, and the goals of the Marx party, and proposes an alternative while presenting the issues inherent in the application of Marxism. Is this presentation, or others like it, appropriate for a philosophical question on the topic if Mein Kampf were the center of the question and discussion? The question is, namely, can we discuss "philosophies" or does this necessarily need to be "philosophies as presented by philosophers"?
On the one hand, we can't too sharply restrict our topics to merely a single brand of philosophical
chosen ones (everything here is in "how sharply" we can restrict it).
On the other hand, this place doesn't work as an SE or have any topical unity if it is a generic
anything thought about anything domain (which would seem to be a consequence of opening the door to anything that is in some sense philosophical -- the hinge here is on the "philosophical" bit and its scope).
Obviously I'd rather err more towards the former than the latter because the latter to me has the more destructive consequences for this SE. It would seem to make it so that nothing is ever off-topic except on easily contestable grounds. But I do think the reality has to be some where in between.
So, a narrowly focused critique of marxism on largely philosophical grounds in Mein Kampfe seems like it could be on topic if we're being asked to work through the accuracy of its interpretation of marxism. Conversely, I'd suppose (having not read it) there are large sections of it that are completely off-topic and not about "philosophy" in any normal construal of the word.
On Demarcations of Philosophy and Meta of Philosophy Stack Exchange
I am going to argue more on the liberal and "looser" side of this topic, namely philosophies of non-philosophers.
Personally, I would argue philosophy is more a style of inquiry rather than a field of specific knowledge. On the other hand, canon and/or academic philosophy is a field of knowledge.
Philosophy does not have a (strong, at least) demarcation to begin with. It thus overlaps with literature, history, theology, politics; etc., etc.; more than folks realize.
This is evidenced by the fact that there is a sub-field of philosophy dedicated to discussing the epistemology and thus demarcations of philosophy.
This sub-field is known as meta-philosophy, and is sometimes described as "philosophy of philosophy."
"Why do I have a throat infection?"
 Medicine might cite a type of bacteria and poor health-hygiene.
 A philosopher could state that suffering serves a type of function in the universe.
I would argue philosophy is more a style of inquiry rather than a field of specific knowledge; consider statement .
The style of inquiry here is different depending on the field on study. However, bacteria and/or infections are not normally a topic in academic and/or canon philosophy.
In regards to metaphilosophy: Even then academic philosophy is already extremely broad in-of-itself. You can try browsing the table of contents at the SEP.
I reference the topic of quantum computing to show how broad academic philosophy can get.
I present an example of a borderline case here:--
Sources and References:--
Other References and Further Reading:--
"Philosopher" is merely an honorific term. Especially when "philosophy" is used in the sense of "a way of looking at things" even the likes of Karl Marx, Ayn Rand, Jacques Derrida, Slavoj Žižek, or fictional characters like Socrates, Morpheus, Gandalf, Jesus et cetera can be considered "philosopher".
When philosophy is used in the sense of the translation from the Greek, all one need do is reject false argument, rationally assess the truth value of claim(s), or advance knowledge claim(s) for minimally adequate use of philosopher as descriptor. Philosophy is, after all, respect for obtaining knowledge and this translation has stood for 2500+ years. One is a philosopher (or not) on basis of the nature of the propositions and method of verification (or falsification) employed. And the same with philosophy. The language of philosophy and the language of poetry (or manifesto) are logically and epistemologically distinct. The former deals with "what is", the latter with "what is to you"; the former deals with hypotheses, the latter with sentiment; the former concerned with advancing a hypothesis, the latter trafficking a weltanschauung; the former is confirmed by verification, the latter by agreement. And as regards agreement: were that the proper basis for determining "what is", the earth would be flat and you could sail off.
Philosophy is something you do regardless of whether or not considered a philosopher. Marx's or Hitler's characterization of a state of affairs to serve their competing weltanschauung, however, are not philosophy.