The tendency to ignore or downplay the shortcomings of an individual, group, or item while focusing primarily on the positive aspects is often referred to as "idealization" or "rosy retrospection." This cognitive bias allows people to perceive something more favorably than it may inherently be, often overlooking flaws or negative traits.
Another related concept is "confirmation bias," where individuals favor information that supports their pre-existing beliefs or feelings, leading them to dismiss or ignore contradictory evidence.
In some contexts, this behavior can also be described as "noble cause corruption," where the perceived good of an individual’s actions overshadows their unethical behavior.
Overall, these biases can heavily influence opinions and decisions, impacting how people evaluate and form judgments about others.