The phrase "bark up the wrong tree" is an idiomatic expression used to convey the idea of accusing or blaming someone who is innocent or not responsible for a particular situation. It means that someone is directing their criticism or blame in the wrong direction.
While the phrase itself is not inherently impolite, its usage can be perceived as impolite or confrontational depending on the context and tone in which it is used. It can come across as accusatory or dismissive if used in a disrespectful or aggressive manner.
If you're concerned about politeness, it's generally advisable to choose your words carefully and consider the impact they may have on others. It's important to communicate your thoughts and concerns in a respectful and constructive manner, rather than using phrases that may be interpreted as confrontational or rude.