It's hard to quantify negative impact of future dealings, but it's even harder to say Booking.com should change their methods when the people aware enough to be annoyed continue to give them money. It's like complaining about Google following you around the web and using GMail.
Either the alternatives just aren't good enough or the negative externalities not severe enough to change consumer behavior. Either of those considerations could change, but until they do it's hard to argue Booking.com should reduce current earnings. Not when people who book a room above a bar that plays music into the early morning blame themselves for not reading the fine print...