Are manners something that any human should know only by logic?

No, manners are not something that humans know only by logic. Let me explain this to you clearly. Yes, there are certain basic manners and behaviors that are logical and obvious to any human being. The Torah itself tells us that even without the Written Torah, we could learn modesty from the cat, honesty from the ant, and proper conduct from other animals. Rabbi Yochanan says that if the Torah had not been given, we would still learn these basic behaviors from creation itself. Hashem created the world in such a way that certain things are logically obvious - murder is wrong, theft is wrong, adultery is wrong. You don't need to be a scholar to know these things. You were created in the image of God, which means you have the ability to use common sense and know the difference between right and wrong. However, and this is critical, logic alone is not enough. Here's the problem: whatever logic you have is biased based on your own life and your own experiences. You are not the world. Human logic is flawed and subjective. That's why we need Torah to teach us the complete picture of how to behave. Good manners are not automatic just because you keep Shabbos or wear a kippah or attended yeshiva. Manners, like yirat shamayim and all good character traits, are something you have to work on in order to acquire. This is why we must learn Mussar - the ethical teachings of Torah that show us how to develop proper character traits and apply them correctly. Without Torah and Mussar, you will not know when to be merciful and when not to be merciful, when to be kind and when it's forbidden to be kind. You need both - the logical understanding of basic right and wrong, and the Torah's guidance to know how to apply it properly in every situation. A person who relies only on their own logic, without Torah, will eventually turn their morals into evil because they lack the complete framework. This is why the Gemara says that if you see someone who knows Torah but has bad manners, you should run away from that person and befriend someone who is ignorant but has good manners. Why? Because the person with good manners can be taught Torah and will use it properly. But someone who learned Torah and still has bad manners - this person is worse than a dead animal in the street. He doesn't even know how to use the Torah. So the answer is: basic logic gives you a foundation, but you absolutely need Torah and Mussar to develop complete, proper manners and know how to behave as a true servant of Hashem. One without the other is insufficient and even dangerous.