Not all advocates of liberty agree with you that the two are mutually exclusive. Here are five excellent pro-monarchy articles by libertarians, published in libertarian sources:
Erik von Kuehnelt-Leddihn, Monarchy and War
Lew Rockwell, Why Hate Monarchs?
Sean Gabb, In Defence of the Monarchy
Carlo Stagnaro, In Honor of Franz Joseph
Leland Yeager, Monarchy: Friend of Liberty
...not to mention an entire book by economist Hans-Hermann Hoppe, Democracy--The God that Failed: The Economics and Politics of Monarchy, Democracy, and Natural Order
Thanks for reminding me why I'm not a Libertarian.