Get the log out of your eye. Several Yankee states wanted the slave trade to continue and voted to extend the deadline to 1808, viz: Massachusetts, New Hampshire & Connecticutt.
The Constitution could not be passed without the 3/4 rule and that was a Southern demand.
http://www.americanhistory.com/history/ShortHistory/shorthistory6.mgi#Chapter_17
185. Compromise as to the Slave-Trade.--When the subject of the powers to be given to Congress came to be discussed, there was even greater excitement. The Northerners wanted Congress to have power to regulate commerce. But the Southerners opposed it because they feared Congress would use this power to put an end to the slave-trade. John Rutledge of South Carolina even went so far as to say that unless this question was settled in favor of the slaveholders, the slave states would "not be parties to the Union." In the end this matter also was compromised by providing that Congress could not prohibit the slave-trade until 1808. These were the three great compromises. But there were compromises on so many smaller points that we cannot even mention them here.