There are many reasons to remove stitching... the most common is that they are not straight. It is only necessary to remove the stitches that are not straight not all of the sewing.
Start at one end of the stitches you would like to remove. Insert the tip of the seam ripper between the thread and the fabric, keeping the seam ripper perpendicular to the fabric. Gently pull the seam ripper upward away from the fabric to cut the thread.
Repeat at the opposite end of the stitching you want to remove.