He wants to take Aarti to the finale with him. He also feels for her. Just see the clip when it was announced Aarti was eliminated. The way Aarti hugged and Sid responded. Best hug of season with lots of feeling.
And fight with Aarti is just to show her on screen. To show that she can speak up. I guess, Sid and Aarti is a team which they have worked from outside.