It is important to respect a sim. Remember, when someone opens their sim to the public that's like opening their home to you. They are getting vulnerable for your benefit. That Resident is spending RL Currency for your benefit. It is just respectful to be sensitive to that by respecting the sim rules, wearing the sim tag or a inoffensive tag and wearing an avatar that is in keeping with the sim motif.
It is also respectful for the sim owner to understand someone may have a Role Play that is different from their sim when they leave. That sim owner does not have the right to reject you from their sim for what you do in a different sim (Unless what you do is against the TOS, CS or Local Laws). Although they do have the right to eject you for being offensive to the sim's purpose or occupants.