How should you deal with plagiarism? Help, please!

So....I found out that someone has been happily copying my story "Operation Beautiful" off of Quizilla and posting it as "Operation Smile." It is kind of amusing, to me, that they copied off of quizilla instead of Mibba. Especially because Mibba gets posted on faster and I've already mentioned in the quizilla chapters that I post on Mibba. Anyway, I sent them a "strongly worded letter" and was hoping you guys could let me know of I'm dealing with it properly.

Hello :)

Just wanted to let you know that i saw your story...or should I say my story. ^^
I'm already posting it on this site as "Operation Beautiful." I'm pretty sure you know this is plagiarism, and that plagiarism is illegal, and I would really appreciate it if you took the story down.

Thanks,
Worldclass

Too soft? Too harsh? Lol. I'm almost feeling flattered that my story was good enough that they felt inclined to copy it.