For a short recount on the for/against camp, I recommend
this article. It is in no way comprehensive, considering its length, yet it gives good starting point for debate. Guess which side has more scientific arguments?
Oh, and it's the medieval warm period. The little ice age was later on, during 17-19th centuries. The fact that Europe was overpopulated at the time of the Black death is because of the warmer climate and consequently the surprisingly high amount of grain produced considering their "primitive" farming techniques.
Edit: Thank you Neon.