To my understanding from reading that book, in negotiation we aim to listen to our counterpart and treat them as a partner, and not as an enemy.

You try to listen to them, and communicate in such a way so as to create a win-win situation.

By really listening and empathizing with them, you are able to ask the right questions so they give you extra information about their situation, which you can use to understand what they want and explore potential solutions.

People aren't always aware on the moment of exactly what they want or need, so they can't articulate it perfectly. With understanding the situation, you can usually propose a solution that works for both parties. So, in that sense, I'm sure people still like you, as long as you up hold a respectful and communicatively open attitude.

So I don't think people would have a negative opinion of you if you have used the practices from the book in your negotiation.

The idea of the book is that "splitting the difference" is just a lazy and avoidant way to negotiate. Instead, we should work with the adversary to find the best solution for both, which according to the author, is more about emotions than reasoning.