The primary thing to consider, then, is what is being attacked. Is it the reader or the idea?
Common communication wisdom would tell you to attack the idea, not the reader. So would basic graciousness. Attacking the reader is the quickest way to undermine the effectiveness of your own message by alienating the very person to whose you are communicating.
But I suggest the best way to communicate is to attack your readers, not just ideas.
I don't mean ad hominem attacks. Nor do I mean condescension or insult.
Instead, attack your reader in his mind and heart. The ideas are the means through which you do this. You must dig into the emotions and the thought processes of the reader. You must unseat them from the place of comfortable apathy. The ideas are the channel into the reader’s life in which, upon your arrival, you can wreak havoc with the aim of change, growth, and betterment.
If all you attack is the idea you allow readers to distance themselves from the engagement. Instead of leading to change it becomes merely an intellectual exercise of discourse or disagreement. Instead of a bettered person you get a practiced intellectual tennis player able to return all idea volleys. If all you attack are ideas it is too easy for the reader to release your ideas from their minds and to be released by them.
Demand and cajole. Plead and prod. Persuade and push. Attack with every ounce of gracious creative conviction you can find. And always communicate in such a way that, when the reader is finished with your work, he feels as if you have finished with him and he is the creative work.