The first two lines of The Speech to the Virginia Convention are:
"Mr. President: No man thinks more highly than I do of the patriotism, as well as abilities of the very worthy gentlemen who have just addressed the house. But different men often see the same subject in different lights; and, therefore, I hope that it will not be thought disrespectful to those gentlemen, if, entertaining as I do opinions of a character very opposite to theirs, I shall speak forth my sentiments freely and without reserve.
One persuasive technique in these few lines is the acknowledgment and almost concession to the opposition. What he is trying to accomplish is to engage the people who do not feel the same way that he does regarding military involvement with the British. It is important to him to convince those who currently disagree with him, and beginning his speech appealing to them and their patriotism provides an "olive branch" of sorts. Appealing to the opposite side is smart, acknowledging their patriotism so that they will listen to his appeals and hopefully be convinced. Had he started his speech by accusing them of being unpatriotic, they would not have listened to the rest of his speech and he would most definitely not gain any momentum for his cause.