Rant doesn't necessarily have negative connotations for me either, it really depends on the context. Your usage didn't look pejorative at all to me. It's sort of like a less intensive version of "vitriol" and there is no problem (implied) if the target deserves it (or is presented so).

It is similar to the word "extremist", the technical definition is rarely only what people mean to invoke, and it's acquiring further connotations.

Losing precise meaning is the way to newspeak, and it distresses me. It is sometimes the result of being uncomfortable with or incapable of discussing specific facts, which is harder than the inside view.