While proxy measurements can't give us an exact measure of past temperatures, I still believe they are a very good indication of past climate, especially when you consider that several of the different methods used correlate very closely with each other.

These proxy measurements actually show a moderate medieval warm period, so "accounts" saying it was warm during that time frame actually match the proxy data quite well, and the sources do not contradict each other.

Furthermore, any "accounts" from the medieval times about a warm period cannot give us a completely accurate representation of the temperature of that time period either. The warm period began around 800 and continued through around 1300AD. However, the first form of thermometer was invented by Galileo in 1593, almost 300 years after the warm period ended.