"Donate to a different charity" is in no way a viable alternative.
Charities are anything but interchangeable. You might not want to sponsor one on ideological grounds, or concerns about how effectively they use the money, or just because you were seeking to support a specific cause. If you deposited money in a box that said "we're buying medicine for sick people in Somaliland" and they sent it to the RSPCA instead, wouldn't you be pissed?
