Past words/deeds may indicate what you can expect in the future. Assuming that's true is unwise. Unless you investigate how do you KNOW?

It is always better to investigate/evaluate/review things on their own merit rather than simply relying on what occurred in the past. People can change. They are not made of stone. They are not necessarily rigid, unadaptable, uneducable. Assuming  is what many people do to their detriment. Do you? Why?