sounds like you just have air in the line, it should feel firm 1/2 way pressed in. bleed the line (may take a few tries), i suggest removing the 2 rear bolts holding down the line (one on the swingarm, one holding the tire hugger), remove the entire caliper and elevating it, attach a hose to the nipple and elevate it higher than the caliper. Works best with 2 people. bleeding the rear can be a pain b/c the line is in a U shape, which will trap air in the middle.
Don't be a road crayon, pavement does not care how cool you think you look in a t-shirt and shorts.