Windows XP is nearly 14 years old and there have been three (soon to be four) new versions of Windows since its inception. As mentioned above, it's also no longer supported by Microsoft. Instead of getting angry at the moderators of a game shard for doing what's best to protect their users, perhaps it'd be more productive to channel that energy into getting your computer upgraded. Yeah, it's a pain, but certainly worth the cost considering using XP now leaves your computer open to all kinds of malicious viruses, malware, etc.
This is not something TOC crew just sprang at the last minute either. They announced the change a year or so beforehand, so there was plenty of warning.
Besides, who's to say that Cyan won't do the same with MOULa in the near future for the same reason? Will people get angry at them too for doing what's best for security?