Explanation

It was difficult to tell whether his tirade in fact had force of fact means that it was difficult tell whether someone’s angry speech (fulmination) was actually true. It is hard to tell whether his speech is “motivated by malice” (that is, “malicious lies,” or aspersion) or “reportorial” information (muckraking “exposing corruption”) that should actually be listened to.

Note that calumny is similar to aspersion and cannot work in the third blank — while the second blank describes negative speech meant to cause harm to others, the third blank describes negative speech that exposes the truth.

Fulmination, aspersion, muckraking.
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Sandy
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