I don't see how taking money away from these companies and then telling them to do something more expensive by enforcing more responsible ways of making palm oil is an answer.
It seems that if you take away money from these companies, you'd inspire them to cut corners to turn profits. Their shareholders dictate profitability.
If you want to encourage good behavior, you should just contact them and tell them you are concerned and ask what they are doing about it to end this problem in a short timeframe. Ask them what you can do to help stop it. They will probably appreciate the help. If they don't respond, write another letter and give them a timeline, like the end of 2016, and tell them if they cannot make a change in the local behavior there by then, you will start a lifetime ban on their products in your family and tell your friends, social media, and the press about your decision.
In general though, banning products hurts workers and shareholders. It doesn't enact the change you want.