Daf Yomi - Beitzah 8- Performing a positive and negative commandment simultaneously

The Gemara states that a positive commandment will override a negative commandment when both commandments are performed simultaneously. It is noteworthy that the Gemara in Sota states that a mitzvah cannot extinguish an aveira, a sin, yet an aveira can extinguish a mitzvah. Apparently, the principle that a positive commandment can override a negative commandment is not a contradiction to this Gemara. Perhaps the idea is that when one performs an aveira intentionally, he has rebelled against HaShem, and it is not possible for one to appease HaShem with a mitzvah when he has just committed an act of rebellion. When one is simultaneously overriding the negative commandment by performing a positive commandment, however, he is demonstrating that he is fully aware that he is performing a negative commandment, yet he is permitted by the Torah to override the negative commandment. This principle allows him to perform the positive commandment and be rewarded for its performance.