Right, you dislike phony validation.
When it's real, you won't notice it. What you'll probably experience is just "an honest actor" or "a good guy" or "someone like me." And the things that person says which are disagreements you experience as "an interesting point I hadn't thought of", etc...
So the advice isn't "put on the performance of validating", rather "find it in yourself to see legitimacy in the other person's situation so you can take interest and listen to them openly".
Yes. And you won't always be able to do that, because you won't always feel that way. Even then, some (honest) sense of your own fallibility and basic respect for where the person might be coming from can help.