What is the origin of the idiom "tar someone or something with the same brush" and when to use it?

The origin of the phrase "tar someone or something with the same brush" can be traced back to the practice of using brushes to apply tar or paint to surfaces. In this context, if one brush was used to apply tar to a particular object, it would inevitably carry traces of the tar. If another object was subsequently painted with the same brush, it would also acquire those traces, regardless of whether or not it deserved the same treatment. It is commonly employed in discussions related to prejudice, stereotypes, discrimination, or biased judgments.