When you doubt someone else’s integrity or intention, you may have valid reasons for feeling that way. These reasons may stem from past experience with these people or previous similar experience or experiences.
Having said this, one also has to look within to see if this reaction is something to do with our own baggage.
You do not want to be stupid and get fooled by others. At the same time, you do not want to impose judgements on others that are inaccurate, which can negatively affect you.
What is a better approach?
Keep your guard up to protect you from being fooled. However, go deeper within yourself to see if these feelings come from others’ behavior or your own paradigm.