You know that feeling of satisfaction when you finish soldering both rows of header pins? You go to pick up the board and oh yes, you've soldered it wrong, definitely, but we can fix it. Please note the following technique is not perfect and does pose risks. Primarily the risk of permanently damaging your board, but it usually works. Use sharp diagonal cutters to divide the black stabilizers into strips. Then use needle nose pliers to slide them off leaving only bare pins. For each of those remaining pins, use needle nose pliers to get a good grip on the longer end. Then heat the top side pad with your iron, and when the solder melts, smoothly remove the pin. It's quite satisfying really. Use copper wick to clean up any remaining solder on the board. And look at that, it's like nothing even happened.