I found this on tumblr and remember reading this in A Distant Mirror. Honestly this sounds like a bunch of preposterous bullhonkey and absurdly reductivist towards the complexities of Medieval Europe, but i was wondering how true this is.
Can you provide some examples of what Tuchman is defining as "juvenile behavior" in that context? Just on the surface I'd be inclined to agree with you that it sounds absurd, but I'd be interested to know regarding what that statement is being made.