I used to argue with a more strident, arrogant tone than I try to adopt now. One influence in changing my tone was Ben Franklin's autobiography:

"I wish well-meaning, sensible men would not lessen their power of doing good by a positive, assuming manner, that seldom fails to disgust, tends to create opposition, and to defeat everyone of those purposes for which speech was given to us, to wit, giving or receiving information or pleasure. For, if you would inform, a positive and dogmatical manner in advancing your sentiments may provoke contradiction and prevent a candid attention."

He describes how he cultivated "the habit of expressing myself in terms of modest diffidence; never using, when I advanced any thing that may possibly be disputed, the words certainly, undoubtedly, or any others that give the air of positiveness to an opinion; but rather say, I conceive or apprehend a thing to be so and so; it appears to me, or I should think it so or so, for such and such reasons; or I imagine it to be so; or it is so, if I am not mistaken.

...

When another asserted something that I thought an error, I deny'd myself the pleasure of contradicting him abruptly, and of showing immediately some absurdity in his proposition; and in answering I began by observing that in certain cases or circumstances his opinion would be right, but in the present case there appear'd or seem'd to me some difference, etc. I soon found the advantage of this change in my manner; the conversations I engag'd in went on more pleasantly. The modest way in which I propos'd my opinions procur'd them a readier reception and less contradiction; I had less mortification when I was found to be in the wrong, and I more easily prevail'd with others to give up their mistakes and join with me when I happened to be in the right."

Another influence was Yvain's How To Not Lose An Argument. The common part of Franklin and Yvain's advice is to phrase your message in such a way that minimal status will be lost by your opponent agreeing with you. Your opponent must not see (consciously or subconsciously) your rhetoric as an attempt to gain status at zir expense.