I recently changed my wiper blades having previously only replaced the rubber refills. It seemed that the blade arm was held in place only by the coil spring against the dome end of the pin. I put the wipers in the vertical position by turning off the ignition & placed a thick cloth under to protect the screen. I then used long nosed pliers on the pin end & against the metal part of the blade. I reckoned so long as I didn't damage the pin, the other part was going anyway. You could use a squirt of WD40 or similar as it looks like theres a little corrosion in that area. The blade should spin on the pin. It may help removal to rotate to a different position.Once I had clicked the dome end inside the coil, it was just a matter of wiggling it off.
Hope that helps. Steve.