I wonder if the people signing this would also boycott anything run or owned by Middle Eastern royalty where laws that Card promotes both exist and are enforced.
On the one side you can retreat to the woods and live off of roots and berries trying not to do any direct harm. But then, depending on your privilege, you leave on the table so many opportunities to steer the ship of society in a less harmful direction.
Or, at the other end of the spectrum you can yield all reaponsibility for your direct actions, instead throwing yourself into the wheeling and dealing of systems of harm, trying to invest what privilege you have to gain leverage so that you can make a bigger difference, focusing only on some theoretical calculus of your global influence, measuring yourself by your imagined net global effect.
Or, more likely, you pick something in between. In the end, we all make a personal decision about what we are willing to sacrifice.
I often use oil, even though I know it's harmful, because I think my boycott of it would cost the world more than it would gain. I could be wrong, but that's my best guess based on my (flawed) understanding of my self and my world.
And I may boycott Ender's Game and I do not think that's hypocritical. It's just an acknowledgement that there are limits to our power and we must choose our battles.