is someone who aggressively argues their point of view and is purposely contentious.
"The word is derived from the Greek meaning warlike, hostile."
In and of itself, polemic is neither positive nor negative, however, since the view may seem radically different to society at the time, it is usually thought to be negative since it goes against the status quo.
However, over time, the view may become appreciated, accepted, and main stream.
An example of this is Martin Luther's Ninety-five Theses which at the time was considered heresy and resulted in his ex-communication from the Catholic Church and being declared an outlaw. The ultimate result has been all the Protestant denominations of Christian faith and a vernacular Bible.
Was Luther a thorn in the side of the Catholic Church? Yes.
Is he now considered a great man? Yes.
Is his soul burning in hell? Probably not.